Intervertebral implants, systems, and methods of use

ABSTRACT

An intervertebral implant frame that is configured to engage a spacer can include a pair of arms that extend longitudinally from a support member such that the arms engage the spacer. The spacer can be made from bone graft, and include a first spacer body made of cortical bone, and a second spacer body made of cancellous bone.

BACKGROUND

Implants for spinal fusion typically include a spacer to allow forgrowth of bone between adjacent vertebral bodies while restoring andmaintaining intervertebral space height that is defined between thevertebral bodies. In some cases, a plate is used to provide stabilityduring healing so as to allow the patient to quickly resume an activelifestyle. The profile of the plate, which is placed on the anterioraspect of the vertebral bodies, however, can lead to dysphasia orpatient discomfort which has precipitated the development of what'sknown as “zero-profile” devices. One example of a conventionalminimal-profile intervertebral implant is insertable substantiallyentirely into the intervertebral space so as to not substantially extendbeyond the footprint of the vertebral bodies that define theintervertebral space.

Other intervertebral implants have been utilized that include a frameshaped in a manner so as to interface with a spacer made from PEEK. Suchspacer bodies typically are customized to have complimentary features tothe frame so that the spacer bodies may be affixed to the frame. Suchframes may not be desirable for spacer bodies made from allograft,however, because allograft spacer bodies may vary in shape, may notinclude the complimentary features needed to be affixed to the frame,and may degrade or resorb overtime.

SUMMARY

In accordance with one embodiment, an intervertebral implant isconfigured to be inserted into an intervertebral space. Theintervertebral implant can include a spacer and a frame. The spacer, inturn, can include a cortical spacer body comprising a cortical bonegraft material, and a cancellous spacer body comprising a cancellousbone graft material. The cancellous spacer body can be disposed proximalwith respect to at least a portion of the cortical spacer body. Theframe can include a support member disposed proximal with respect to thecancellous spacer body and configured to extend along a portion of thecancellous spacer body, such that the cancellous spacer body is disposedbetween the support member and the at least a portion of the corticalspacer body. The frame can further include first and second opposed armsthat extend from the support member and are configured to engage thecortical spacer body.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofembodiments of the application, will be better understood when read inconjunction with the appended drawings. For the purposes of illustratingthe methods, implants and systems of the present application, there isshown in the drawings preferred embodiments. It should be understood,however, that the application is not limited to the precise methods,implants, and systems shown. In the drawings:

FIG. 1A is a perspective view of an intervertebral implant assembly thatis implanted in an intervertebral space defined by a superior vertebralbody and an inferior vertebral body, the intervertebral implant assemblyincluding an intervertebral implant and at least a pair of fixationelements that attach the intervertebral implant to the superiorvertebral body and the inferior vertebral body, respectively;

FIG. 1B is a side elevation view of the intervertebral implant assemblyas shown in FIG. 1A, the intervertebral space defining ananterior-posterior midline;

FIG. 1C is a top plan view of the inferior vertebral body shown in FIG.1B;

FIG. 2A is a perspective view of the intervertebral implant illustratedin FIGS. 1A and 1B, the intervertebral implant having an intervertebralimplant frame and a spacer retained by the intervertebral implant frame;

FIG. 2B is a top plan view of the intervertebral implant shown in FIG.2A;

FIG. 2C is a top plan view of an intervertebral implant similar to FIG.2B, but showing the frame secured to the spacer in accordance with oneembodiment;

FIG. 2D is a top plan view of an intervertebral implant similar to FIG.2C, but showing the frame secured to the spacer in accordance withanother embodiment;

FIG. 2E is a top plan view of an intervertebral implant similar to FIG.2D, but showing the frame secured to the spacer in accordance with yetanother embodiment;

FIG. 2F is a top plan view of an intervertebral implant similar to FIG.2B, but showing the frame secured to the spacer in accordance with stillanother embodiment;

FIG. 3A is a perspective view of the intervertebral implant frame shownin FIG. 2, the intervertebral implant frame having a support member, afirst arm extending from the support member, and a second arm extendingfrom the support member, the first and second arms configured toelastically flex away from each other;

FIG. 3B is a front elevation view of the intervertebral implant frameshown in FIG. 3A;

FIG. 3C is a top plan view of the intervertebral implant frame shown inFIG. 3A;

FIG. 3D is a side elevation view of the intervertebral implant frameshown in FIG. 3A;

FIG. 3E is a cross-sectional view of the intervertebral implant frameshown in FIG. 3D through the line 3E-3E;

FIG. 3F is another perspective view of the intervertebral implant frameshown in FIG. 3A;

FIG. 4A is a perspective view of one embodiment of the fixation elementsthat is configured to affix the intervertebral implant shown in FIG. 2to a vertebral body as illustrated in FIGS. 1A and 1B;

FIG. 4B is a side elevation view of the of the fixation element shown inFIG. 4A;

FIG. 5A is a perspective view of an intervertebral implant systemconstructed in accordance with an embodiment, the system including anactuation instrument configured as an expansion instrument that includesan actuation grip illustrated as an expansion grip that is configured toactuate the frame shown in FIG. 3A from a first configuration to asecond configuration whereby the frame is configured to receive aspacer, for example of the type shown in FIG. 2A;

FIG. 5B is a perspective view of the expansion instrument shown in FIG.5A, the expansion instrument including a first expansion arm and asecond expansion arm coupled to the first expansion arm at a firstpivot, each expansion arm having a handle portion and a gripping portionthat combine to define a handle of the expansion instrument and theexpansion grip illustrated in FIG. 5A;

FIG. 5C is a top plan view of the expansion instrument shown in FIG. 5B;

FIG. 5D is a detailed view of one of the gripping portions of theexpansion instrument shown in FIG. 5B;

FIG. 5E is an enlarged top plan view of the expansion grip shown in FIG.5B, coupled to the first and second arms of the frame shown in FIG. 3A,showing the expansion instrument actuated from a first position to asecond position, whereby the expansion grip applies an expansion forceto the first and second arms of the frame when the expansion instrumentis in the second position, the expansion force biasing the first andsecond arms of the frame to flex away from each other;

FIG. 5F is a perspective view of an expansion instrument in accordancewith another embodiment, shown coupled to the intervertebral implantframe;

FIG. 5G is a perspective view of a first member of the expansioninstrument illustrated in FIG. 5F

FIG. 5H is a perspective view of a second member of the expansioninstrument illustrated in FIG. 5F

FIG. 5I is a sectional end elevation view of the expansion instrumentillustrated in FIG. 5F, shown coupled to the intervertebral implantframe;

FIG. 5J is a sectional plan view of the expansion instrument illustratedin FIG. 5F, shown coupled to the intervertebral implant frame;

FIG. 6A is a perspective view of a spacer of the type illustrated inFIG. 2A, including a cortical spacer body and a cancellous spacer body,and a force transfer member that extends through the cancellous spacerbody and at least into the cortical spacer body;

FIG. 6B is another perspective view of the spacer illustrated in FIG.6A;

FIG. 6C is a top plan view of the spacer illustrated in FIG. 6A;

FIG. 6D is a sectional side elevation view of the spacer illustrated inFIG. 6A;

FIG. 6E is a top plan view of the cancellous spacer body illustrated inFIG. 6A;

FIG. 6F is a perspective view of the cancellous spacer body illustratedin FIG. 6E;

FIG. 6G is another perspective view of the cancellous spacer bodyillustrated in FIG. 6E;

FIG. 6H is a perspective view of the cortical spacer body illustrated inFIG. 6A;

FIG. 6I is a top plan view of the cortical spacer body illustrated inFIG. 6H;

FIG. 6J is a perspective view of the force transfer member illustratedin FIG. 6A;

FIG. 6K is a sectional side elevation view of the spacer as illustratedin FIG. 6A, but including parallel top and bottom surfaces;

FIG. 6L is a sectional side elevation view of the spacer illustrated inFIG. 6A, but showing an aperture extending through the cortical spacerbody and including angled (e.g. lordotic) top and bottom surfaces;

FIG. 6M is a sectional side elevation view of the spacer illustrated inFIG. 6L, but including parallel top and bottom surfaces;

FIG. 7A is a perspective view of a spacer as illustrated in FIG. 6A, butincluding surface geometry in accordance with an alternative embodiment;

FIG. 7B is a perspective view of a spacer as illustrated in FIG. 7A, butincluding surface geometry in accordance with an another embodiment;

FIG. 7C is a perspective view of a spacer as illustrated in FIG. 6A, butincluding surface geometry in accordance with an another embodiment;

FIG. 7D is a perspective view of a spacer as illustrated in FIG. 7C, butincluding surface geometry in accordance with an another embodiment;

FIG. 7E is a perspective view of a spacer as illustrated in FIG. 7D, butincluding surface geometry in accordance with an another embodiment;

FIG. 7F is a perspective view of a spacer as illustrated in FIG. 7E, butincluding surface geometry in accordance with an another embodiment;

FIG. 8A is a top plan view of the spacer as illustrated in FIG. 6A, butincluding engagement members constructed in accordance with analternative embodiment;

FIG. 8B is a sectional side elevation view of the spacer illustrated inFIG. 8A;

FIG. 9A is a top plan view of the spacer as illustrated in FIG. 6A, butincluding engagement members constructed in accordance with an anotheralternative embodiment;

FIG. 9B is a sectional side elevation view of the spacer illustrated inFIG. 9A;

FIG. 10A is a top plan view of the spacer as illustrated in FIG. 6A, butconstructed in accordance with yet another alternative embodiment;

FIG. 10B is a sectional side elevation view of the spacer illustrated inFIG. 10A;

FIG. 11A is an exploded perspective view of a spacer similar to thespacer illustrated in FIG. 6A, but constructed in accordance with analternative embodiment;

FIG. 11B is a top plan view of an intervertebral implant including aframe attached to the spacer illustrated in FIG. 11A;

FIG. 11C is a to plan view of an intervertebral implant including aframe attached to a spacer constructed in accordance with an alternativeembodiment;

FIG. 11D is a perspective view of the spacer illustrated in FIG. 11C;

FIG. 12A is a perspective view of an intervertebral spacer constructedin accordance with an alternative embodiment, including groovesconfigured to engage the intervertebral implant frame illustrated inFIG. 3A;

FIG. 12B is another perspective view of the intervertebral spacer asillustrated in FIG. 12A, but including smooth opposed lateral surfacesso as to engage an intervertebral implant frame in accordance with analternative embodiment;

FIG. 12C is an exploded perspective view of the intervertebral spacerillustrated in FIG. 12B;

FIG. 12D is another exploded perspective view of the intervertebralspacer illustrated in FIG. 12B;

FIG. 12E is a schematic front elevation view of the intervertebralspacer of FIGS. 12A and 12B, showing apertures created by fixationelements that extend through the frame and into the correspondingvertebral body; and

FIG. 12F is a schematic front elevation view showing apertures createdby fixation elements that extend through the frame and into thecorresponding vertebral body, the apertures configured in accordancewith an alternative embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, a superior vertebral body 10 a defines afirst or superior vertebral surface 14 a of an intervertebral space 18,and an adjacent second or inferior vertebral body 10 b defines aninferior vertebral surface 14 b of the intervertebral space 18. Thus,the intervertebral space 18 is disposed between or otherwise defined bythe vertebral bodies 10 a and 10 b. The vertebral bodies 10 a and 10 bcan be anatomically adjacent vertebral bodies, or can remain after aportion of bone has been removed. The intervertebral space 18 can bedisposed anywhere along the spine as desired, including at the lumbar,thoracic, and cervical regions of the spine. As illustrated, theintervertebral space 18 is illustrated after a discectomy, whereby thedisc material has been removed or at least partially removed to preparethe intervertebral space 18 to receive an intervertebral implant 22. Asshown, the intervertebral implant 22 can be affixed to the superior andinferior vertebral bodies 10 a and 10 b with respective fixationelements 62. The intervertebral implant 22 and the fixation elements 62together define an intervertebral implant assembly 24.

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inner” or “distal” and “outer” or “proximal” refer to directionstoward and away from, respectively, the geometric center of the implantand related parts thereof. The words, “anterior”, “posterior”,“superior,” “inferior,” “medial,” “lateral,” and related words and/orphrases are used to designate various positions and orientations in thehuman body to which reference is made and are not meant to be limiting.The terminology includes the above-listed words, derivatives thereof andwords of similar import.

The intervertebral implant 22 is described herein as extendinghorizontally along a longitudinal direction “L” and lateral direction“A”, and vertically along a transverse direction “T”. Unless otherwisespecified herein, the terms “lateral,” “longitudinal,” and “transverse”are used to describe the orthogonal directional components of variouscomponents. It should be appreciated that while the longitudinal andlateral directions are illustrated as extending along a horizontalplane, and that the transverse direction is illustrated as extendingalong a vertical plane, the planes that encompass the various directionsmay differ during use. For instance, when the intervertebral implant 22is implanted into the intervertebral space 18 along an insertiondirection I, the transverse direction T extends vertically generallyalong the superior-inferior (or caudal-cranial) direction, while thehorizontal plane defined by the longitudinal direction L and lateraldirection A lies generally in the anatomical plane defined by theanterior-posterior direction, and the medial-lateral direction,respectively. Thus, the lateral direction A can define themedial-lateral direction when the implant 22 is implanted in theintervertebral space. The longitudinal direction L can define theanterior-posterior direction when the implant 22 is implanted in theintervertebral space. Accordingly, the directional terms “vertical” and“horizontal” are used to describe the intervertebral implant 22 and itscomponents as illustrated merely for the purposes of clarity andillustration.

As shown in FIGS. 1B and 1C, the vertebral surfaces 14 a and 14 b of thevertebral bodies 10 a and 10 b can define a geometrical centroid M thatis generally located at an anterior-posterior midpoint between ananterior end and a posterior end of the surfaces 14 a and 14 b. As shownin FIG. 1B, the intervertebral implant 22 is configured to be disposedor otherwise implanted in the intervertebral space 18 such that aportion of the intervertebral implant 22 is located on a posterior sideof a medial lateral plane that intersects the centroid M, and a portionof the intervertebral implant 22 is located on an anterior side of themedial lateral plane that intersects the centroid M.

In reference to FIGS. 1A, 1B, 2A and 2B, the intervertebral implant 22includes an intervertebral implant frame 26 and an intervertebral spacer30 that is retained by the frame 26. In one example, the spacer 30 isconfigured to be received by the frame 26. Thus, it can be said that theframe 26 is configured to receive the spacer 30. The intervertebralimplant 22, defines a proximal end P and a distal end D. The distal endD is spaced from the proximal end P in a distal direction, which isalong the longitudinal direction L. When the intervertebral implant 22is implanted in an intervertebral space, the proximal end P can definean anterior end, and the distal end D can define a posterior end spacedfrom the anterior end in an anterior-posterior direction. Theintervertebral implant 22 is configured to be inserted into theintervertebral space in an insertion direction. In one example, theinsertion direction can be in the distal direction, such that the distaldirection can be referred to as an insertion direction into theintervertebral space. It should be appreciated, of course, theintervertebral implant 22 can be inserted into the intervertebral spacealong any suitable direction as desired, for instance in the lateraldirection A. Alternatively, the intervertebral implant 22 can beinserted in an oblique direction that includes both the distal directionand the lateral direction A. Thus, the insertion direction can be in atleast the distal direction, which can include the distal direction andthe oblique direction. Further, it should be appreciated that theintervertebral implant 22 is configured to be inserted into the thoracicregion, and the lumbar region of the spine. Further, it should beappreciated that the intervertebral implant 22 is configured to beinserted into the thoracic region, and the lumbar region of the spine.Conversely, the proximal end P is spaced from the distal end D in aproximal direction that is opposite the distal direction, and also isalong the longitudinal direction L. The frame 26 may be made from anybiocompatible material, such as TAN alloy, or PEEK. The spacer 30 can becomposed of a bone graft such as allograft bone, autograft bone orxenograft bone. It should be appreciated that the spacer 30 can furtherinclude ceramics, polymers, metals, and biomaterials. In particular, thespacer 30 can include a cortical spacer body 410 made of cortical bonegraft material, and a cancellous spacer body 412 made of cancellous bonegraft material. By using a spacer 30 composed of bone graft, surfacearea for fusion can be maximized with respect to synthetic spacers.Additionally, the bone graft promotes bony in-growth of the respectivevertebral bodies into the spacer 30, and increased probability and speedof sound fusion between the spacer and the respective vertebral bodies.The frame 26 is configured to be attached to various bone graft spacerfootprint geometries, which may or may not conform to the internalfootprint of the frame 26. It should be further appreciated that theinsertion direction can be in the distal direction, and that the distaldirection can be oriented in a lateral approach into the intervertebralspace, an anterior-posterior approach into the intervertebral space, oran oblique approach into the intervertebral space. The oblique approachcan be oblique to both the anterior-posterior approach and the lateralapproach.

As shown in FIGS. 3A-3E the frame 26 includes a support member 34, afirst arm 38 that extends from the support member 34, and a second arm42 that extends from the support member 34. In the illustratedembodiment, the first and second arms 38 and 42 are flexible arms thatextend from opposed ends of the support member 34 such that the supportmember 34, the first arm 38, and the second arm 42 together create athree wall structure that retains and secures the spacer 30 to the frame26.

As shown in FIGS. 3A-3C, the support member 34 includes a body 46 thatdefines an inner surface 50, an outer surface 54, and at least one, suchas two or such as four, fixation element receiving apertures 58 thatextend through the body 46 from the outer surface 54 to the innersurface 50. Each fixation element receiving aperture 58 is configured toreceive a respective fixation element, such as fixation element 62 shownin FIGS. 4A and 4B. While the fixation elements 62 are illustrated asscrews, it should be appreciated that the fixation elements 62 may alsobe nails or any other fixation element configured to attach theintervertebral implant 22 to the first and second vertebral bodies 10 aand 10 b. As shown, the support member 34 can further include at leastone tab 64 such as a plurality of tabs 64 that extend from the body 46generally along the transverse direction T. For instance, the supportmember 34 can include three tabs 64. The tabs 64 may be disposed at ananterior side of the vertebral bodies and prevent over-insertion of theframe 26 into the intervertebral space 18. In the illustratedembodiment, the support member 34 includes a pair of superior tabs 64that extend in an upward or superior direction from the body 35, and aninferior tab 64 that extends in a downward or inferior direction fromthe body 35. Each of the tabs 64 can be configured to sit flush orslightly proud of an anterior surface of the vertebral bodies dependingon the patient's spinal anatomy and/or site preparation. It should beappreciated, however, that the support member 34 can include otherconfigurations for the tabs 64. For example, the support member 34 caninclude a single superior tab 64 and a pair of inferior tabs 64.Alternatively still, as described in more detail below with respect toFIG. 3F, the support member can include a pair of superior tabs and apair of inferior tabs.

As shown in FIG. 3B, two of the fixation element receiving apertures 58are inner apertures 66 that extend through the body 46 at a downwardangle relative to the insertion direction I, and two of the fixationelement receiving apertures 58 are outer apertures 70 that extendthrough the body 46 at an upward angle relative to the insertiondirection I. The inner apertures 66 are configured to receive respectivefixation elements, such as fixation element 62 shown in FIGS. 4A and 4B,to thereby attach the intervertebral implant 22 to the inferiorvertebral body 10 b. Similarly, the outer apertures 70 are configured toreceive respective fixation elements 62 to thereby attach theintervertebral implant 22 to the superior vertebral body 10 a. It shouldbe appreciated, however, that the inner apertures 66 can extend throughthe body 46 at an upwards angle and the outer apertures 70 can extendthrough the body 46 at a downwards angle, as desired. Moreover, itshould be appreciated that the support member 34 can define any numberof fixation element receiving apertures 58 as desired. It should beappreciated that the fixation element receiving apertures 58 can beconfigured as boreholes sized to accommodate the fixation elements 62,or can be configured as recesses or a partial boreholes in order toaccommodate the fixation elements 62.

As shown in FIG. 3B, the apertures 58 each define internal threads 78.The internal threads 78 are configured to engage external threads 80defined by a head 82 of the respective fixation element 62 (see FIGS.4A-4B) that is received within the apertures 58, such that the internalthreads 78 mate with the external threads 80. It should be appreciated,however, that the apertures 58 can be void of threads as desired. Theorientation of the apertures 58 may be configured such that the fixationelements that are received by the apertures 58 may have an insertionvariance of +/−5 degrees and do not allow toggling or settling. Oncefully received, the fixation elements may lock to the frame 26 tothereby increase the surgeon's reassurance of good screw trajectoriesand can act as a safety by preventing possibilities of over-insertionduring implantation.

As shown in FIG. 3C, support member 34 can include an abutment member 73that extends from the inner surface 50 along the distal direction. Itwill be appreciated that the abutment member 73 can be configured toabut a force transfer member 424 (see FIG. 6D) of the spacer 30 thatreceives forces from the frame 26, and transfers the received forces tothe cortical spacer body 41, as will be described in more detail below.In certain embodiments, the abutment member 73 can further be sized tobe inserted into a force transfer channel 418 (see FIG. 6B) in thecancellous spacer body 412 so as to abut the force transfer member 424.The abutment member 73 is illustrated as a spike though it should beappreciated, that the abutment member 73 can have other shapes asdesired. For instance, the abutment member 73 can have a pointed or arounded abutment surface that abuts the force transfer member 424 asdesired.

As shown in FIGS. 2A, and 3A-3E, the first arm 38 and the second arm 42each extend from the support member 34 and define a first distalterminal end 83 and a second distal terminal end 84, respectively. Thefirst and second arms 38 and 42 each define gripping portions andsupport portions. The gripping portions are configured to retain thespacer 30 while the support portions are configured to support thevertebral bodies 10 a and 10 b relative to each other. The grippingportions and the support portions can be a single structure or thesupport portions can be separate structures that extend from thegripping portions. The arms 38 and 42 can be radiolucent so as toincrease fluoroscopy visibility. The first arm 38 includes a first innerspacer contacting surface 88 and the second arm 42 includes a secondinner spacer contacting surface 92 that is spaced from the first innerspacer contacting surface 88 along a first direction, such as thelateral direction A. The inner surface of the support member 34, thefirst inner spacer contacting surface 88, and the second inner spacercontacting surface 92 together define a void 94 that is configured toreceive and grip the spacer 30. The terminal ends 83 and 84 are spacedapart from the support member along a second direction, such as thelongitudinal direction L that is substantially perpendicular to thefirst direction so as to define first and second lengths L₁ and L₂,respectively of the first and second arms 38 and 42. The first andsecond arms 38 and 42 are sized such that the first and second lengthsL₁ and L₂ are each greater than a length L₃ defined between an anteriorend E of the inferior vertebral body 10 b and the centroid M of thesurface 14 b of the inferior vertebral body 10 b, as shown in FIG. 1C.It should be appreciated, that the first and second arms 38 and 42 canalso be sized such that the first and second lengths L₁ and L₂ aregreater than a length defined between an anterior end of the superiorvertebral body 10 a and a centroid of the surface 14 a of the superiorvertebral body 10 a. The first and second lengths L₁ and L₂ may bebetween about 3.5 mm and about 12 mm, between about 6.0 mm and about 10mm, and preferably about 9.5 mm. In some embodiments, the support member34, the first arm 38, and the second arm 42 extend around at least 51%of the spacer 30, and preferably around at least 80% of the spacer 30.

The flexible arms 38 and 42 can have a transverse height and a lateralwidth that at least partially define a cross-sectional area of the arms38 and 42. The arms 38 and 42 can have a cross-sectional area that mayvary so long as the arms 38 and 42 are capable of elastically deformingor flexing to thereby allow the frame 26 to receive the spacer andsubsequently apply a retention force to the spacer 30 after the frame 26has received the spacer 30. In that regard, the arms 38 and 42 areconfigured to elastically flex laterally outwardly away from each other,or otherwise elastically deform from a first position to a second flexedposition to allow the frame 26 to receive the spacer 30. It should beappreciated that the first position can be a relaxed position of thearms 38 and 42 or a flexed position of the arms 38 and 42 that isoutwardly flexed with respect to a relaxed position. At least respectiveportions of the arms 38 and 42, such as contact locations 320 and 324(see FIG. 6E), are further spaced from each other in the second positionthan when in the first position. Once the spacer 30 is disposed betweenthe arms 38 and 42, the arms 38 and 42 may flex inwardly toward eachother to a third or engaged position whereby the arms 38 and 42 engagethe spacer 30 so as to secure the frame 26 to the spacer 30 as shown inFIG. 2. It should be appreciated that the third position can beoutwardly flexed with respect to the first position, and can besubstantially equal to the first position. Thus, the respective portionsof the arms 38 and 42 can be further spaced from each other when in thethird position with respect to the first position, or the respectiveportions of the arms 38 and 42 can be spaced from each other when in thethird position a distance substantially equal to the distance that therespective portions of the arms 38 and 42 are spaced when in the firstposition. Thus, it can be said that when the arms 38 and 42 are in thethird position, at least respective portions of the arms 38 and 42 arespaced apart a distance equal to or greater than (or no less than) thedistance that the arms 38 and 42 are spaced when in the first position.It will be further appreciated from the description below in accordancewith certain embodiments (see, for instance FIG. 14C) that at leastrespective portions of the arms 38 and 42 can be spaced apart a distancewhen in the engaged position that is less than the distance that therespective portions of the arms 38 and 42 are spaced apart when in thefirst position.

As shown in FIG. 3C, the first and second arms 38 and 42 extend from thesupport member 34 such that the first and second arms 38 and 42 areangled toward each other so as to push the spacer 30 toward the other ofthe first and second arms 38 and 42 and toward the support member 34.For example, the inner surface of the support member 34 and the firstinner spacer contacting surface 88 form an angle Ø₁ that is less than 90degrees, and the inner surface 50 of the support member 34 and thesecond inner spacer contacting surface 92 form an angle Ø₂ that is lessthan 90 degrees. In the illustrated embodiment, Ø₁ and Ø₂ are each about88 degrees, though it should be appreciated that Ø₁ and Ø₂ may be anyangle as desired, and may be different angles with respect to eachother.

As shown in FIGS. 3C and 3D, each arm 38 and 42 includes a substantiallystraight portion 100 that extends from the support member 34, and adistal bent or angled portion 104 that extends from a distal end of thestraight portion 100 toward the other of the bent portions 104 such thatthe bent portions 104 are configured to contact a distal surface of thespacer 30. As shown, the bent portions 104 at least partially wraparound the spacer 30 to thereby prevent the spacer 30 from separatingfrom the frame 26 after the spacer 30 has been retained by the frame 26.As shown in FIG. 3A, each arm 38 and 42 can include at least oneretention member 116, such as a plurality of retention members 116 thatextend out from the first and second inner spacer contacting surfaces 88and 92. The retention members 116 can be arranged in a respective firstcolumn supported by the first arm 38, and a second column supported bythe second arm 42. In the illustrated embodiment, the retention members116 define teeth that extend out of the bent portions 104 so as to forma column of teeth on each bent portion 104. The retention members 116are configured to engage the spacer 30 when the frame 22 is retainingthe spacer 30 to thereby ensure that the spacer 30 remains retained bythe frame 22. It should be appreciated, however, that the retentionmember 116 can have any configuration as desired, so long as theretention member 116 is capable of engaging the spacer 30. For example,the retention members 116 can be configured as spikes that extend fromthe inner surfaces 88 and 92 at an angle, elongate blades, punches thatcan be punched into the spacer 30 by an individual after the spacer 30is disposed in the frame 26, or any suitable roughened surface,grit-blasted surface, or knurled surface that is configured to engagethe spacer 30 and thereby retain the spacer 30.

Referring to FIG. 6A, the spacer 30 defines a proximal end surface 30 aand a distal end surface 30 b that is spaced from the proximal endsurface 30 a in the distal direction along the longitudinal direction L.The spacer 30 further defines a pair of opposed side surfaces 30 cspaced from each other along the lateral direction A. The spacer 30further defines a top surface 30 d and a bottom surface 30 e spaced fromthe top surface 30 d in the transverse direction T. The spacer 30 candefine a plurality of grooves 415 that can extend into the side surfaces30 c at the cortical spacer body 410, and the distal end surface 30 b.The grooves can extend at least into the spacer 30 along the transversedirection T, and can extend through the spacer 30 along the transversedirection T. The retention members 116 supported by the first arm 38 areconfigured to be inserted into the grooves 415 at a first one of theside surfaces 30 c. The retention members 116 supported by the secondarm 42 are configured to be inserted into the grooves 415 at the secondone of the side surfaces 30 c.

Referring now to FIGS. 3C-3D and 2C, the retention members 116 candefine a proximal surface 116 a and a distal surface 116 b that eachextend from the respective inner surfaces 88 and 92 of the correspondingfirst and second arms 38 and 42. The proximal surface and distalsurfaces 116 a and 116 b can converge toward each other and can adjoineach other at a tip 116 c. The proximal surface can define a concavityas illustrated in FIG. 2C. The distal surface 116 b be substantiallylinear. For instance, the distal surface 116 b can be oriented along thelateral direction A. The tip 116 c can be offset in the distal directionwith respect to a location of the inner surface from which the proximalsurface 116 a extends. As illustrated in FIG. 2D, the proximal surface116 a can be substantially linear. For instance, the proximal surface116 a can be angled with respect to the lateral direction A. In oneexample, the proximal surface 116 a can be oriented so as to extend inboth the distal direction and the lateral direction A as it extends fromthe respective inner surface toward the tip 116 c. The distal surface116 b can be convex as it extends from the respective inner surfacetoward the tip 116 c. Referring to FIG. 2E, the proximal surface 116 abe substantially linear. For instance, the proximal surface 116 a can beoriented along the lateral direction A. The distal surface 116 b can beconvex as it extends from the respective inner surface toward the tip116 c. As illustrated in FIG. 2F, the proximal surface 116 a can beconcave as it extends out from the respective inner surface toward thetip 116 c. The distal surface 116 b can be convex as it extends out fromthe respective inner surface toward the tip 116 c. The tip 116 c can beoffset in the proximal direction with respect to a location of the innersurface from which the proximal surface 116 a extends. Each of theretention members 116 can overlap the spacer within the groove 415 byany distance as desired. For instance, each of the retention members 116can overlap the spacer within the groove 415 by a distance between andincluding approximately 0.5 mm and approximately 4.0 mm. As a functionof the length of the spacer 30 along the longitudinal direction L, theoverlap can be within the range of 25% and 100% of the length of thespacer 30 in the longitudinal direction L. For instance, the overlap canbe within the range of 40% and 80% of the length of the spacer 30 in thelongitudinal direction L.

As shown in FIG. 3D, the arms 38 and 42 may be configured to assist inbearing compressive loads by the vertebral bodies 10 a and 10 b tothereby mitigate subsidence and settling. As shown, each arm 38 and 42defines a respective distal portion 110 and a respective proximalportion 114. The distal portions 110 are spaced apart from the proximalportions 114 along the longitudinal direction L such that when the frame26 is disposed in the intervertebral space 18, the distal portions 110are on the posterior or distal side of the centroid M of the surface 14b of the inferior vertebral body 10 b, and the proximal portions 114 areon the anterior or proximal side of the centroid M of the surface 14 bof the inferior vertebral body 10 b. Each distal portion 110 can definea superior vertebral body contacting surface 118 and an inferiorvertebral body contacting surface 122. Similarly, each proximal portion114 can define a superior vertebral body contacting surface 126 and aninferior vertebral body contacting surface 130. Because of the length ofthe arms 38 and 42 and because of the transverse height of the arms 38and 42 at their distal and proximal portions, the frame 26 can bearcompressive loads from the vertebral bodies if the spacer 30 were tocompress.

As shown in FIG. 3D, the arms 38 and 42 may be configured to conform tothe lordotic curve of the spine and in particular of the intervertebralspace 18 in which the frame 26 is to be disposed. For example, a linedrawn between the superior vertebral body contacting surfaces 118 and126 of the first arm 38 forms an angle that is between about 0 degreesand about −5 degrees with respect to the insertion direction I, and aline drawn between the inferior vertebral body contacting surfaces 122and 130 of the first arm forms a line that is between about 0 degreesand about 5 degrees with respect to the insertion direction I.Similarly, a line drawn between the superior vertebral body contactingsurfaces 118 and 126 of the second arm 42 forms an angle that is betweenabout 0 degrees and about −5 degrees with respect to the insertiondirection, and a line drawn between the inferior vertebral bodycontacting surfaces 122 and 130 of the second arm 42 forms an angle thatis between about 0 degrees and about 5 degrees with respect to theinsertion direction I. It should be appreciated, however, that the linesdrawn between the superior vertebral body contacting surfaces 118 and126, and between the inferior vertebral body contacting surfaces 122 and130 can be any angle as desired. For example, the lines may be parallelto each other. Therefore, it can be said that a first plane is definedby the superior vertebral body contacting surfaces, and a second planeis defined by the inferior vertebral body contacting surfaces. The firstplane and the second plane can be parallel to each other or convergetoward each other.

As shown in FIG. 3D, each arm 38 and 42 can further include a superiorcut-out 140 and an inferior cut-out 144 to thereby provide visual accessto the superior vertebral body 10 a and to the inferior vertebral body10 b respectively when the frame 26 is disposed in the intervertebralspace 18. The cut-outs 140 and 144 are each disposed between theproximal portions 114 and distal portions 110 of the first and secondarms 38 and 42. As shown, the superior cut-outs 140 extend laterallythrough an upper portion of the arms 38 and 42 so as to define uppercurved recesses 148 in the straight portions 100 of the arms 38 and 42.Similarly, the inferior cut-outs 144 extend laterally through a lowerportion of the arms 38 and 42 so as to define lower curved recesses 152in the arms 38 and 42. It should be appreciated that the superior andinferior cut-outs 140 and 144 can have other configurations as desired.For example, the cut-outs 140 and 144 can define rectangular channelsthat extend through the arms 38 and 42.

As shown in FIGS. 3D and 3E, each arm 38 and 42 can further include awindow 156 that extends laterally through the straight portions 100 ofthe arms 38 and 42 between the superior and inferior cut-outs 140 and144. The windows 156 are configured to provide visual access to thespacer 30 through the first and second arms 38 and 42 when the frame 26is retaining the spacer 30. As shown, the windows 156 are oval shapedand elongate along the longitudinal direction L. It should beappreciated, however, that the windows 156 can have any shape asdesired. For example, the windows 156 can also be rectangular shaped.

As shown in FIGS. 3A, 3D, and 3E, each arm 38 and 42 can include anengagement member 170 that is configured to receive a first and a secondexternal expansion force, respectively, from an expansion instrumentprior to insertion of the spacer 30 into the void 94 such that at leastone of the first and second arms 38 and 42 elastically expands orelastically flexes with respect to the other of the first and secondarms 38 and 42 in response to the expansion forces. As shown in FIG. 3A,the engagement members 170 each define a dove-tailed slot 174 thatdefines an opening 178 at its distal end such that the expansioninstrument can engage the dove-tailed slot 174 in a direction that isopposite to the insertion direction I of the frame 26, thereby securingthe expansion instrument to the dove-tailed slot 174. As shown in FIG.3D, the dove-tailed slots 174 are wider at the openings 178 and taper asthey extend proximally. The wider openings 178 provide a guide for theexpansion instrument to engage the engagement members 170. As shown inFIG. 3A, the dove-tailed slots 174 each include a pair of opposedrecesses 182 that define angled engagement surfaces 186. It should beappreciated, however, that the engagement members 170 can have anyconfiguration as desired so long as they can receive respectiveexpansion forces.

Referring now to FIG. 3F, and as descried above, the support member 34can include at least one tab 64, for instance a plurality of tabs 64,that extend from the body 46. In one example, the tabs 64 can include atleast a first tab 64 a and a second tab 64 b that each extends from thebody 35 in the upward or superior direction. Thus, the first and secondtabs 64 a and 64 b can be referred to as a first pair of tabs. The firsttab 64 a and the second tab 64 b can be spaced from each other along thelateral direction A, such that the support member 34 defines a first gap65 a between the first and second tabs 64 a and 64 b along the lateraldirection. The first gap 65 a can be sized or otherwise configured toreceive a portion of the first vertebral body when the first and secondarms 38 and 42 are inserted into the intervertebral space. Inparticular, the first tab is spaced from second tab 64 b by a firstdistance G1 along the lateral direction A. The first distance G1 can beany distance so long as a portion of the first vertebral body can extendinto the gap 65 a.

With continued reference to FIG. 3F, the tabs 64 can include at least athird tab 64 c and a fourth tab 64 d that each extends from the body 35in the downward or inferior direction. Thus, the third and fourth tabs64 c and 64 d can be referred to as a second pair of tabs. The third tab64 c and the fourth tab 64 d can be spaced from each other along thelateral direction A, such that the support member 34 defines a secondgap 65 b between the third and fourth tabs 64 c and 64 d along thelateral direction. The second gap 65 b can be sized or otherwiseconfigured to receive a portion of the second vertebral body when thefirst and second arms 38 and 42 are inserted into the intervertebralspace. In particular, the third tab 64 c is spaced from fourth tab 64 dby a second distance G2 along the lateral direction A. As shown, thesecond distance G2 can be less than the first distance G1. It should beappreciated, however, that the first and second distances G1 and G2 cansubstantially the same or the second distance G2 can be greater than thefirst distance G1, as desired. The first and second tabs 64 a and 64 bcan be equidistant from a centerline of the frame 26, and the third andfourth tabs 64 c and 64 d can be equidistant from the centerline of theframe 26. The centerline of the frame can extend in the transversedirection T and bifurcate the frame 26 in the lateral direction A. Itshould be appreciated, however, that the tabs 64 can be alternativelypositioned as desired. Each of the third and fourth tabs 64 c and 64 dcan be spaced from the centerline a distance that is less than thedistance that each of the first and second tabs 64 a and 64 b is spacedfrom the centerline.

Each of the tabs 64 a-64 d defines a front surface and an opposed bonecontacting surface. The front surfaces of each tab 64 a-64 d can beflush with or otherwise coincident with the outer surface 54 asillustrated. It should be appreciated, however, that the front surfacescan be offset with respect to the outer surface 54 as desired. The bonecontacting surfaces of the first and second tabs 64 a and 64 b areconfigured to abut the first vertebral body and the bone contactingsurfaces of the third and fourth tabs 64 c and 64 d are configured toabut the second vertebral body when the first and second arms 38 and 42are inserted into the intervertebral space. When the frame 26 isimplanted into the intervertebral space, anterior surfaces of the firstand second vertebral bodies can extend into the first and second gaps 65a and 65 b. Further, the first and second vertebral bodies can be flushwith or extend beyond the front faces of the tabs 64 a-64 d.Accordingly, it can be said that the frame 26 provides a zero profile ata centerline of the vertebral bodies when the arms 38 and 42 areinserted into the intervertebral space. The frame 26, and alternativeembodiments thereof, are described in U.S. patent application Ser. No.13/767,097 filed Feb. 14, 2013, the disclosure of which is herebyincorporated by reference as if set forth in its entirety herein.

As shown in FIGS. 5A-5E, the spacer 30 can be coupled to the frame 26using an actuation instrument 210 that is configured as an expansioninstrument. The instrument 210, the frame 26, and in some cases thespacer 30 can together define an intervertebral implant system 214. Theexpansion instrument 210 includes a grip 212 and a handle 213. The grip212 is configured as an expansion grip and is configured to apply thefirst and second expansion forces to the engagement members 170 of thefirst and second arms 38 and 42. The first and second expansion forceswill elastically expand the first and second arms 38 and 42 of the frame26 to thereby allow the spacer 30 to be received by the void 94 of theframe 26.

As shown, the instrument 210 includes a first arm 220 that is configuredto releasably couple to the first arm 38 of the frame 26, and a secondarm 224 that is rotatably coupled to the first arm 220 at a first pivot228 and is configured to releasably couple to the second arm 42 of theframe 26. The first and second arms 220 and 224 are configured asexpansions arms. The first and second expansion arms 220 and 224 arepivotally coupled to each other at the first pivot 228 such thatrotation of the first and second expansion arms 220 and 224 about thefirst pivot 228 causes the first and second arms 38 and 42 of the frame26 to elastically flex away from each other when the instrument 210 iscoupled to the frame 26. Therefore, the instrument 210 is configured tohave a first position or configuration whereby the instrument 210 can becoupled to the frame 26, and a second position or configuration wherebythe instrument 210 is applying expansion forces to the arms 38 and 42 ofthe frame 26 so that the frame can receive the spacer 30.

As shown in FIGS. 5B and 5C, each expansion arm 220 and 224 includes ahandle portion 232 that extends proximally from the first pivot 228 anda gripping portion 236 that extends distally from the first pivot 228.The handle portions 232 define the handle 213, and the gripping portions236 define the grip 212. The handle portions 232 are configured to begripped by an individual such that the handle portions 232 can besqueezed or otherwise moved toward each other. The expansion instrument210 can further include a handle locking mechanism 240 that isconfigured to lock the handle portions 232 relative to each other afterthe handle portions 232 have been moved toward each other. In theillustrated embodiment, the locking mechanism 240 includes a threadedshaft 244 and a nut 248. As at least one of the handle portions 232 ismoved along the shaft 244, the nut 248 can be threaded along the shaft244 to thereby lock the handle portions 232 relative to each other. Itshould be appreciated, however, that the locking mechanism 240 caninclude other configurations, as desired. For example, the lockingmechanism 240 can have a ratchet configuration.

As shown in FIGS. 5C and 5D, the gripping portions 236 are configured toexpand the frame arms as the handle portions 232 are moved toward eachother. Each gripping portion 236 includes an extension member 250 thatextends distally from the first pivot 228, and a gripping member 254that is pivotally coupled to a distal end of the extension member 250 ata second pivot 258. Each gripping member 254 includes an engagementmember 262 that is configured to engage respective engagement members170 of the first and second arms 38 and 42 of the frame 26. As shown inFIG. 5D, the engagement members 262 are dove-tailed members 266 that areopposed to each other and are configured to mate with the dove-tailedslots of the first and second arms 38 and 42 to thereby couple theexpansion instrument 210 to the frame 26. As shown, each dove-tailedmember 266 includes a pair of transversely opposed protrusions 280 thateach defines an angled engagement surface 284 that is configured to abutor otherwise contact a respective angled engagement surface 186 of theslots 174 when the engagement members 262 are mated with the engagementmembers 170. It should be appreciated that the engagement members 262can have other configurations as desired. For example, the engagementmembers 262 and the engagement members 170 can be reversed.

As shown in FIG. 5D, a proximal end of each engagement member 262defines a tapered lead-in portion 270 that allows the engagement members262 to easily be guided into the openings 178 of the engagement members170. Therefore, the expansion instrument 210 can easily be coupled tothe frame 26 along a direction that is opposite the insertion directionI. That is, if the frame 26 is stationary, the expansion instrument 210can be coupled to the frame 26 by translating the instrument 210 along adirection that is opposite the insertion direction I.

As shown in FIG. 5C, each gripping member 254 includes a pair of stops300 that extend proximally toward the extension member 250 and arespaced apart from the extension member 250. As the gripping member 254rotates about the second pivot 258 the stops 300 will limit the rotationby contacting the extension member 250. Therefore, the angular range inwhich the gripping members 254 can rotate about the second pivots 258will depend on the distance in which the stops 300 are spaced apart fromthe extension members 250.

As shown in FIG. 5C, each gripping portion 236 further includes abiasing member 304 that is configured to bias the gripping members 254toward each other. In the illustrated embodiment, the biasing members304 are leaf springs 308 that are coupled to the extension members 250and urge against an outer surface of the gripping members 304. Bybiasing the gripping members 254 toward each other, the expansioninstrument 210 can more easily and more predictably be coupled to theframe 26. It should be appreciated, however, that the biasing members304 can have other configurations as desired. For example, the biasingmembers can be elastically flexible wires and can be disposed within thegripping members 254 as desired.

In operation and in reference to FIG. 5E, the expansion instrument 210is coupled to the frame 26 by placing the engagement members 262 of theinstrument 210 distal to the engagement members 170 of the frame 26. Bytranslating or otherwise moving the frame 26 or the instrument 210toward the other, the engagement members 262 will engage the engagementmembers 170 to thereby couple the frame 26 to the instrument 210 suchthat the second pivots 258 of the instrument 210 abut an outer surfaceof the flexible arms 38 and 42 proximate to the support member 34. Bysqueezing the handle portions 232 toward each other, the extensionmember 250 of the first expansion arm 220 will rotate counterclockwiseabout the first pivot 228 and the gripping member 254 of the firstexpansion arm 220 will rotate clockwise about the second pivot 258.Conversely, the extension member 250 of the second expansion arm 224will rotate clockwise about the first pivot 228 and the gripping member254 of the second expansion arm 224 will rotate counterclockwise aboutthe second pivot 258.

This rotation will cause at least one of the first and second arms 38and 42 to elastically flex away from the other. For example, the firstand second inner spacer contacting surfaces 88 and 92 of the first andsecond arms 38 and 42 can define respective first and second respectivecontact locations 320 and 324, and at least one of the first and secondarms 38 and 42 is flexible so as to be movable between a first position,whereby the frame 26 defines a first distance d₁ that extends along thelateral direction A between the first and second contact locations 320and 324, and a second position, whereby the frame 26 defines a seconddistance d₂ that extends along the lateral direction A between the firstand second contact locations 320 and 324. It should be appreciated thatthe first and second contact locations 320 and 324 can be locatedanywhere along the arms 320 and 324 so long as they remain the same whenthe first and second distances are measured.

As shown in FIG. 5E, the second distance d₂ is greater than the firstdistance d₁ such that when in the second position, the void 94 defines across-sectional dimension that is greater than that of the spacer 30such that the void 94 is sized to receive the spacer 30. While the arms38 and 42 are elastically flexed, at least one of the arms 38 and 42 isbiased toward the first position. Therefore, when the handle portions232 of the instrument 210 are released, the arms 38 and 42 will flexback to a third position, and when in the third position, the frame 26defines a third distance d₃ that extends along the lateral direction Abetween the first and second contact locations 320 and 324 and is lessthan the second distance d₂ (See FIG. 2B). When in the third position atleast one of the first and second inner contacting surfaces 88 and 92 ofthe arms 38 and 42 will apply a retention force against the spacer 30along a direction toward the other of the first and second inner spacercontacting surfaces 88 and 92.

Referring now to FIGS. 5F-5J, the spacer 30 can be coupled to the frame26 using an actuation instrument 510 that is configured as an expansioninstrument in accordance with an alternative embodiment. Thus, theinstrument 510, the frame 26, and in some cases the spacer 30 cantogether define an intervertebral implant system 514. The expansioninstrument 510 includes first and second members 510 a and 510 b thatare configured to engage each other so as to define a grip 512 and ahandle 523. The grip 512 is configured as an expansion grip and isconfigured to apply the first and second expansion forces to theengagement members 170 of the first and second arms 38 and 42. The firstand second expansion forces will elastically expand the first and secondarms 38 and 42 of the frame 26 to thereby allow the spacer 30 to bereceived by the void 94 of the frame 26.

As shown, the first member 510 a includes a first arm 520 that isconfigured to releasably couple to the first arm 38 of the frame 26. Thesecond member 510 b includes a second arm 524 that is configured toreleasably couple to the second arm 42 of the frame 26. The first andsecond arms 520 and 524 are configured as expansions arms. The first andsecond expansion arms 520 and 524 are pivotally coupled to each othersuch that rotation of the first and second expansion arms 520 and 524with respect to each other about respective pivot locations causes thefirst and second arms 38 and 42 of the frame 26 to elastically flex awayfrom each other when the instrument 510 is coupled to the frame 26.Therefore, the instrument 510 is configured to have a first position orconfiguration whereby the instrument 510 can be coupled to the frame 26,and a second position or configuration whereby the instrument 510 isapplying expansion forces to the arms 38 and 42 of the frame 26 so thatthe frame can receive the spacer 30.

The first member 510 a defines a first base 511 a, such that the firstarm 520 generally extends from the first base 511 a in a distaldirection. The first arm 520 can be monolithic with the first base 511a. For instance, the first base 511 a and the first arm 520 can be madefrom the same material. The material can be metal. Alternatively, thematerial can be plastic. Alternatively, the first arm 520 can beattached to the first base 511 a in any manner desired. In this regard,the first base 511 a and the first arm 520 can be made from differentmaterials. For example, the first base 511 a can be plastic, and thefirst arm 520 can be a metal. Alternatively, the first base 511 a can ametal, and the first arm 520 can be a plastic. The first member 510 acan define a first gap 513 a that extends into the first base so as todefine corresponding first and second portions 515 a and 517 a that areseparated from each other by the first gap 513 a. The first memberportion 515 a can be an upper portion, and the second portion 517 a canbe a lower portion that is spaced from the upper portion 515 a in adownward direction. At least a portion of the first gap 513 a can extendinto the first base 511 a but not through the first base 511 a, so as toterminate at a first stop wall 519 a.

Similarly, the second member 510 b defines a second base 511 b, suchthat the second arm 524 generally extends from the second base 511 b inthe distal direction. The second arm 524 can be monolithic with thesecond base 511 b. For instance, the second base 511 b and the secondarm 524 can be made from the same material. The material can be metal.Alternatively, the material can be plastic. Alternatively, the secondarm 524 can be attached to the second base 511 b in any manner desired.In this regard, the second base 511 b and the second arm 524 can be madefrom different materials. For example, the second base 511 b can beplastic, and the second arm 524 can be a metal. Alternatively, thesecond base 511 b can a metal, and the second arm 524 can be a plastic.The second member 510 b can define a second gap 513 b that extends intothe second base so as to define corresponding first and second portions515 b and 517 b that are separated from each other by the second gap 513b. The first member portion 515 b can be an upper portion, and thesecond portion 517 b can be a lower portion that is spaced from theupper portion 515 b in the downward direction. At least a portion of thesecond gap 513 b can extend into the second base 511 b but not throughthe second base 511 b, so as to terminate at a second stop wall 519 b.

The first gap 513 a can be sized to receive the first portion 515 b ofthe second member 510 b. Alternatively or additionally, the first gap513 can be sized to receive the second portion 517 b of the secondmember 510 b. Similarly, the second gap 513 b can be sized tosimultaneously receive the first portion 515 a of the first member 510a. Alternatively or additionally, the second gap 513 b can be sized tosimultaneously receive the second portion 517 a of the first member 510a. In accordance with one embodiment, the first gap 513 a is sized toreceive the first portion 515 b of the second member 510 b, and thesecond gap 513 b is sized to simultaneously receive the second portion517 a of the first member 510 a. The first and second bases 511 a and511 b slide relative to each other so as to cause the respective firstand second arms 520 and 524 to move away from each other. Otherwisestated, the first and second bases 511 a and 511 b can pivot withrespect to each other about a pivot location that translates as thefirst and second bases 511 a and 511 b translate with respect to eachother.

The first arm 520 is configured to releasably couple to the first arm 38of the frame 26 such that the first member 510 a abuts a first side ofthe frame 26 at a first abutment. The second arm 524 is configured toreleasably couple to the second arm 42 of the frame 26 such that thesecond member 510 b abuts a second side of the frame 26 at a secondabutment. The second side of the frame 26 is opposite the first side ofthe frame 26 with respect to the lateral direction. In accordance withone embodiment, the first arm 520 is configured to releasably couple tothe first arm 38 of the frame 26 such that the first member 510 a abutsa first side of the support member 34 at the first abutment. The secondarm 524 is configured to releasably couple to the second arm 42 of theframe 26 such that the second member 510 b abuts a second side of thesupport member 34 at the second abutment. The first and second members510 a and 510 b of the instrument 510 can be identical to each other inone embodiment. Alternatively, the first and second abutments can bedefined by proximal ends of the first and second arms 38 and 42,respectively.

The first and second members 510 a and 510 b can define first and secondhandle portions 523 a and 523 b, respectively, that define the handle523 of the instrument 510. During operation, the handle portions 523 aand 523 b can be moved toward each other, thereby causing the first gap513 a to further receive the respective portion of the second member 510b, and the second gap 513 b to further receive the respective portion ofthe first member 510 a. The handle portions 523 a and 523 b can definegrips that are engaged and receive a force that biases each of thehandle portions 523 a and 523 b toward the other of the handle portions523 a and 523 b. As the first and second members 510 a and 510 b aremoved toward each other, the first member 510 a pivots about the firstabutment, and the second member 510 b pivots about the second abutment,thereby causing the first and second arms 520 and 524 to move away fromeach other. When the first and second arms 520 and 524 are coupled tothe first and second arms 38 and 42, respectively, of the frame 26,movement of the first and second arms 520 a and 524 away from each othercauses the first and second arms 38 and 42 to move from the firstposition to the second position described above.

The instrument 510 can include a force limiter that limits the amount offorce applied to the first and second arms 38 and 42 of the frame 26that expands the first and second arms 38 and 42 from the first positionto the second position. In particular, the portion of the second member510 b that is received in the first gap 513 a is configured to abut thefirst stop wall 519 a, thereby preventing additional movement of thehandle portions 523 a and 523 b toward each other. Alternatively oradditionally, the portion of the first member 510 a that is received inthe second gap 513 b is configured to abut the second stop wall 519 b,thereby preventing additional movement of the handle portions 523 a and523 b toward each other. Thus, during operation, the handle portions 523a and 523 b can be moved toward each other until one or both of thefirst and second members 510 a and 510 b abuts the second and first stopwalls 519 b and 519 a, respectively.

As described above, the first and second arms 520 and 524 of theinstrument 510 is configured to releasably couple to the first andsecond arms 38 and 42, respectively, of the frame 26 such that movementof the first and second arms 520 and 524 away from each other applies afirst to the first and second arms 38 and 42 that causes the first andsecond arms 38 and 42 to move from the first position to the secondposition. In particular, the instrument 510 defines a grip 512 that isconfigured to releasably couple to the engagement members 170 of thefirst and second arms 38 and 42, respectively, of the frame 26. The grip512 can include gripping portions supported by the first and second arms520 and 524, respectively, that are configured to releasably couple tothe engagement members 170 of the first and second arms 38 and 42,respectively, of the frame 26. The gripping portions 536 are configuredto expand the frame arms 38 and 42 as the handle portions 523 a and 523b are moved toward each other.

Each gripping portion 536, and thus each of the first and second arms520 and 524, can include an engagement member 562 that is configured toengage the respective engagement members 170 of the first and secondarms 38 and 42 of the frame 26, thereby attaching the arms 520 and 524to the first and second arms 38 and 42, respectively. The engagementmembers 562 can be dove-tailed members 566 that are opposed to eachother and are configured to mate with the dove-tailed slots of the firstand second arms 38 and 42 to thereby releasably couple the expansioninstrument 510 to the frame 26. As shown, each of the dove-tailedmembers 566 includes a protrusion 580 such that the protrusions 580 areopposite each other. Each of the protrusions 580 defines an angledengagement surface 584 that is configured to abut or otherwise contact arespective angled engagement surface 186 of the slots 174 when theengagement members 562 are mated with the engagement members 170. Itshould be appreciated that the engagement members 562 can have otherconfigurations as desired. For example, the geometry of the engagementmembers 562 and the engagement members 170 can be reversed. A proximalend of each engagement member 562 can define a tapered lead-in portion570 that allows the engagement members 562 to easily be guided into theopenings 178 of the engagement members 170. Therefore, the expansioninstrument 510 can be inserted into the openings 178 in a firstdirection so as to releasably couple the instrument 510 to the frame 26.Similarly, the expansion instrument 510 can be removed from the openings178 in a second direction opposite the first direction so as to decouplethe instrument 510 from the frame 26. It should be appreciated that theexpansion instrument 510 can be assembled with the frame 26, and thatthe frame 26 can retain the spacer 30 or not retain the spacer 30 whenthe expansion instrument is assembled with the frame 26.

Referring to FIGS. 6A-6D, and the spacer 30 defines a proximal endsurface 30 a and a distal end surface 30 b that is spaced from theproximal end surface 30 a along the longitudinal direction L. Forinstance, the distal end surface 30 b is spaced from the proximal endsurface 30 a in the distal direction. Thus, the distal end surface 30 bcan be spaced from the proximal end 30 a in the insertion direction ofthe spacer 30 into the intervertebral space. Accordingly, the distal endsurface 30 b can be spaced from the proximal end 30 a in the insertiondirection of the intervertebral implant 22 into the intervertebralspace. It should be appreciated that, when the implant 22, and thus thespacer 30, is implanted in the intervertebral space, the distal endsurface 30 b is spaced posteriorly from the proximal end surface 30 a.

The spacer 30 further defines a pair of opposed side surfaces 30 cspaced from each other along the lateral direction A. Each of the sidesurfaces 30 c further extends from the proximal end surface 30 a to thedistal end surface 30 b. When the frame 26 is attached to the spacer 30(see FIGS. 2A-B and 11B-C), the support member 34 can extend along theproximal end surface 30 a, and the arms 38 and 42 can extend along atleast a portion up to an entirety of the length along the longitudinaldirection L of respective different ones of the sides 30 c. It should beappreciated that the surfaces 30 a-30 e can be sized and shaped asdesired. For instance at least one or more up to all of the surfaces 30a-30 e can be planar, curved, bent, or otherwise non-planar as desired.

The spacer 30 further defines a top surface 30 d and a bottom surface 30e spaced from the top surface 30 d along the transverse direction T. Forinstance, the top surface 30 d is spaced upward with respect to thebottom surface 30 e. Thus, the top surface 30 d is configured to facethe superior vertebral surface 14 a of the superior vertebral body 10 a,and contact the superior vertebral surface 14 a of the superiorvertebral body 10 a. The bottom surface 30 e is configured to face theinferior vertebral surface 14 b of the inferior vertebral body 10 b, andcontact the inferior vertebral surface 14 b of the inferior vertebralbody 10 b. The spacer 30 can define a height from the top surface 30 cto the bottom surface 30 d in the transverse direction T. The spacer canfurther define a length from the proximal end surface 30 a to the distalend surface 30 b in the longitudinal direction. The distal end surface30 b can define a first width along the lateral direction A that is lessthan a second width along the lateral direction A of the proximal endsurface 30 a. Each of the first and second widths can extend along thelateral direction A from one of the side surfaces 30 c to the other ofthe side surfaces 30 c. At least one or both of the first and secondwidths can be greater than the height and less than the length.

As described above, the spacer 30 can be made from a bone graft materialsuch as allograft bone, autograft bone, or xenograft bone, for example.For instance, the spacer 30 can include a cortical spacer body 410 and acancellous spacer body 412. The cortical spacer body 410 can define atleast a portion up to an entirety of the distal end surface 30 b. Thecancellous spacer body 412 can define at least a portion up to anentirety of the proximal end surface 30 a. It will be appreciated thatthe a fixation member, such as a screw, that is inserted through thefixation element receiving aperture 58 (see FIGS. 3A-3C) toward thespacer 30 travels from the support member 34 and through the cancellousspacer body 412, and thus through the cancellous bone graft material,without passing through cortical spacer body 410, and thus withoutpassing through any of the cortical bone graft material. Thus, astraight line passing centrally through the fixation element receivingapertures 58 is aligned with the cancellous spacer body 412 withoutfirst passing through the cortical spacer body 410. The cortical spacerbody 410 can further define a first portion of one or both of the sidesurfaces 30 c, and the cancellous spacer body 412 can define a secondportion of one or both of the side surfaces 30 c. The first portion ofthe side surfaces 30 c can be distal with respect to the second portionof the side surfaces 30 c. Similarly, the cortical spacer body 410 canfurther define a first portion of either or both of the top and bottomsurfaces 30 d and 30 e. The cancellous spacer body 412 can define asecond portion of either or both of the top and bottom surfaces 30 d and30 e. The first portion of the top and bottom surfaces 30 d and 30 e canbe distal with respect to the second portion of the top and bottomsurfaces 30 d and 30 e.

The cortical spacer body 410 and the cancellous spacer body 412 areconfigured to abut each other so as to define the spacer 30. Forinstance, the cortical spacer body 410 can include an engagement member414, and the cancellous spacer body 412 can include an engagement member416 that is configured to engage with the engagement member 414 of thecortical spacer body 410 so as to join the cortical spacer body 410 tothe cancellous spacer body 412. In this regard, the engagement member414 of the cortical spacer body 410 can be referred to as a firstengagement member, and the engagement member 416 of the cancellousspacer body 412 can be referred to as a second engagement member. Thefirst engagement member 414 can be disposed distal with respect to thesecond engagement member 416. Further, the first and second engagementmembers 414 and 416 can overlap along the longitudinal direction L suchthat a straight line that extends in the distal direction from theproximal end surface 30 a can pass through both the first engagementmember 414 and the second engagement member 416.

In accordance with one embodiment, the first engagement member 414 candefine a recess 419, and the second engagement member 416 be configuredas a projection 420 that is sized to be received in the recess 419.Otherwise sated, the recess 419 is sized to receive the projection 420.Thus, the recess 419 defined by the first engagement member 414 is sizedto receive the second engagement member 416. The first engagement member414 can be defined by a base 414 a and a pair of necked portions 414 bthat extend out from the base 414 a in the distal direction and projectinward in opposite directions toward each other along the lateraldirection A. The base 414 a and the necked portions 414 b can define therecess 419. The recess 419 can extend through the cortical spacer body410 along the transverse direction T. The second engagement member 416can include a base 416 a and at least one wing 416 b, such as a pair ofwings 416 b, that extend from the base 416 a in the proximal direction,and project out with respect to the stem 416 a in opposite directionsaway from each other along the lateral direction A. The wings 416 b canthus be disposed between the necked portions 414 b and the base 414 a.Similarly, the necked portions 414 b can be disposed between the wings416 b and the base 416 a. Accordingly, the second engagement member 416is surrounded by the first engagement member 414 along the lateraldirection A and in the distal direction. Otherwise stated, the firstengagement member 414 surrounds the second engagement member 416 alongthe lateral direction A and in the distal direction. It can thus be saidthat the cortical spacer body 410 can partially surround the cancellousbody portion 412.

Thus, when the first and second engagement members 414 and 416 engageeach other so as to join the cortical spacer body 410 to the cancellousspacer body 412, the engagement members 414 and 416 interfere with eachother along both the longitudinal direction L and the lateral directionA. The interference thus prevents removal of the cortical spacer body410 and the cancellous spacer body 412 along the longitudinal andlateral directions. Rather, in order to remove the cortical spacer body410 and the cancellous spacer body 412 from each other, the corticalspacer body 410 and the cancellous spacer body 412 are moved withrespect to each other along the transverse direction T until theengagement members 414 and 416 are removed from interference with eachother.

It is recognized that the cortical spacer body 410 provides structuralrigidity to the spacer 30, and the cancellous spacer body 412 promotesbony ingrowth of the first and second vertebral bodies into thecancellous spacer body 412. Accordingly, it is desirable to provide asufficiently high surface area of cancellous spacer body 412 at the topsurface 30 d and the bottom surface 30 e to promote adequate boneyingrowth while providing a sufficient volume of cortical spacer body 412to provide adequate structural rigidity for the spacer 30. The spacer30, constructed in accordance with various embodiments described hereinin with reference to FIGS. 6A-12E, can have a surface area of cancellousbone within a first range between and including approximately 40% andapproximately 85% at either or both of the top and bottom surfaces 30 dand 30 e. For instance, the first range can be between and includeapproximately 40% and 75%, including approximately 55% and 70%. Thus, itcan be said that either or both of the top and bottom surfaces 30 d and30 e can have a surface area, and a majority of the surface area can bedefined by the cancellous spacer body 412. A minority of the surfacearea can be defined by the cortical spacer body 410.

As illustrated in FIG. 6A, the cortical spacer body 410 can define asurface area at each of the top and bottom surfaces 30 d and 30 e asdesired, for instance between 35 mm² and 60 mm², including between 40mm² and 50 mm², for instance approximately 46 mm². The cancellous spacerbody 412 can define a surface area at each of the top and bottomsurfaces 30 d and 30 e as desired, for instance between 50 mm² and 100mm², including between 70 mm² and 90 mm², for instance approximately 816mm². The spacer 30, constructed in accordance with various embodimentsdescribed herein in with reference to FIGS. 6A-12E, can have any heightfrom the top surface 30 c to the bottom surface 30 d as desired. Itshould be appreciated that the spacers 30, and thus the intervertebralimplants 22, described herein can be sized as desired to be insertedinto an intervertebral spacer at any location along the spine, includingthe cervical region, the thoracic region, and the lumbar region.

The spacer 30 further defines a force transfer channel 418 that extendsthrough the cancellous spacer body 412. The force transfer channel 418can terminate at the cortical spacer body 410. Alternatively, thechannel 418 can extend at least into the cortical spacer body 410. Forinstance, the channel 418 can terminate in the cortical spacer body 410.Alternatively, the channel 418 can extend through the cortical spacerbody 410. The channel 418 can have a first opening 418 a defined by theproximal end surface 30 a. Accordingly, the channel 418 can have a firstend defined by the first opening 418 a. The first opening 418 a can bean enclosed opening. That is, the first opening 418 a can be enclosed bythe proximal end surface 30 a along a plane defined by the lateraldirection A and the transverse direction T. The first opening 418 a canbe sized to receive the abutment member 73 of the frame 26 when theframe 26 is attached to the spacer 30. Thus, the abutment member 73 canextend from the first opening 418 a into the channel 418 in the distaldirection.

The channel 418 has a second end opposite the first end. The second endof the channel 418 can be terminate within the cortical spacer body 410as illustrated in FIGS. 6D and 6K, such that the first opening 418 a isthe only opening of the aperture. Alternatively, as illustrated in FIGS.6L and 6M, the channel 418 can have a second opening 418 b defined bythe distal end surface 30 b. Thus, the second end of the channel 418 canbe defined by the second opening 418 b. The channel 418 can thereforeextend from the proximal end surface 30 a to the distal end surface 30b. The second opening 418 b can be an enclosed opening. That is, thesecond opening 418 b can be enclosed by the distal end surface 30 balong a plane defined by the lateral direction A and the transversedirection T. Alternatively, the second end of the channel 418 canterminate at the cortical spacer body 410. Thus, the second opening 418b can be defined by the cancellous spacer body 412. In one example, anentirety of the channel 418 can be enclosed by the spacer 30. That is,the entirety of the channel 418 can be enclosed between the first end ofthe channel 418 and the second end of the channel 418 along a planedefined by the lateral direction A and the transverse direction T. Itshould be appreciated, however, that at least one up to all of the firstopening 418 a, the second opening 418 b, and at least a portion up to anentirety of the channel 418 between the first and second openings 418 aand 418 b can be open, and thus not completely enclosed, along a planedefined by the lateral direction A and the transverse direction T.

In one example, the channel 418 can define a central axis of elongation422 that is equidistant with respect to each of the side surfaces 30 c.The central axis of elongation 422 can therefore bifurcate the spacer 30into two equal halves along the lateral direction A. Thus, the centralaxis of elongation can be oriented in the longitudinal direction L. Itshould be appreciated, however, that the central axis of elongation 422can be oriented in any suitable alternative direction as desired. Forinstance, the central axis of elongation 422 can be elongate in adirection that includes a directional component in the longitudinaldirection L, and one or more directional components in either or both ofthe lateral direction A and the transverse direction T. The channel 418can be cylindrical or can define any suitable alternative shape asdesired.

With continuing reference to FIGS. 6A-6J, the spacer 30 further includesa force transfer member 424 that is configured to be inserted into thechannel 418. Thus, the channel 418 is sized and configured to receivethe force transfer member 424. The force transfer member 424 can be madeof any suitable biocompatible material having a hardness greater thanthe cancellous spacer body 412. For instance, the force transfer member424 can be made of cortical bone, titanium, steel, PEEK, a polymer,ceramics, chronOs, CoCr (or other implantable metals), ultra highmolecular weight polyethylene (UHMWPE), poly ether ether ketone (PEKK),Carbon-fiber reinforced poly ether ether ketone (PEEK), other suitableimplantable polymers, or the like. The force transfer member 424 definesa first end 424 a and a second end 424 b opposite the first end 424 a.The force transfer member 424 can define a length from the first end 424a to the second end 424 b that is less than or equal to the length ofthe channel 418. The length can be straight and linear from the firstend 424 a to the second end 424 b. The force transfer member 424 can becylindrical in one embodiment. For instance, the force transfer member424 can be configured as a dowel. When the force transfer member 424 isdisposed in the channel 418, the first end 424 a can be positionedadjacent the first opening 418 a. In one example, the first end 424 acan be recessed with respect to the first opening 418 a along the distaldirection. In another example, the first end 424 a can be flush with theproximal end surface 30 a. Thus, the first end 424 a can define asurface geometry that matches the surface geometry of the proximal endsurface 30. It should be appreciated that the spacers described hereincan include as many force transfer members 424 as desired. Further, thefirst end 424 a of one or more of the force transfer members 424 can berecessed with respect to the first opening 418 a in the distaldirection. Alternatively or additionally, the first end 424 a of one ormore of the force transfer members 424 can be flush with the proximalend surface 30 a. Referring also to FIG. 3C, the abutment member 73 cancontact the first end 424 a when the frame 26 is attached to the spacer30, and the force transfer member 424 is disposed in the channel 418.For instance, the abutment member 73 can be in abutment with the firstend 424 a along the longitudinal direction L.

Further, when the force transfer member 424 is disposed in the channel418, the second end 424 b can be in contact with the cortical spacerbody 410. In one example, the second end 424 b can be positioned at oradjacent the second end of the channel 418. As described above, thesecond end of the aperture can terminate at the cortical spacer body 410or in the cortical spacer body 410. As a result, the second end 424 b ofthe force transfer member can be in contact with the cortical spacerbody 410. For instance, the second end 424 b can be in abutment with thecortical spacer body 410 along the direction of elongation of the forcetransfer member 424, such as the longitudinal direction L. Alternativelyor additionally, the second end 424 b can be embedded in the corticalspacer body 410. Thus, the second end 424 b can be press-fit in thechannel 418 so as to contact the cortical spacer body 410. The secondend 424 b can be disposed at the second end of the channel 418.Alternatively, the second end 424 b can be recessed with respect to thesecond end of the channel 418, and the distal end surface 30 b, alongthe proximal direction. As described above, the channel 418 canalternatively extend through the spacer body from the proximal endsurface 30 a to the distal end surface 30 b so as to define first andsecond openings 418 a and 418 b. The second end 424 b of the forcetransfer member 424 can extend to the second opening 418 b, and can thusbe flush with the distal end surface 30 b. Accordingly, the forcetransfer member 424 can be press-fit in the channel 418 at the corticalspacer body 410.

During operation, as the intervertebral implant 22 is inserted into theintervertebral space, the outer surface 54 of the body 46 of the supportmember 34 may be impacted by an impaction tool or the like in order toadvance the implant 22 into the intervertebral space. Because theabutment member 73 is in contact with the force transfer member 424, forinstance in abutment contact or in press-fit contact, or both, impactionforces is transferred from the frame 26, to the force transfer member424, through the force transfer member 424, and to the cortical spacerbody 410. Thus, though the support member 34 is positioned adjacent thecancellous spacer body 412, a substantial majority up to a substantialentirety of the impaction forces are absorbed by the cortical spacerbody 412, which has a rigidity greater than that of the cancellousspacer body 412.

Thus, the intervertebral implant can be fabricated by engaging theengagement member 414 of the cortical spacer body 410 with theengagement member 416 of the cancellous spacer body 412, inserting thesecond end 424 b of the force transfer member 424 into the first opening418 a of the force transfer channel 418, inserting the force transfermember 424 in the channel in the distal direction until the second end424 b contacts the cortical spacer body 410, and attaching the frame 26to the spacer 30 such that the support member 34 extends along theproximal end surface 30 a, the abutment member 73 abuts the first end424 a of the force transfer member and the first and second arms 38 and42 engage so as to attach to the respective side surfaces 30 c at thecortical spacer body 410.

It should be appreciated, as illustrated in FIGS. 6D and 6L that the topsurface 30 c and the bottom surface 30 can converge toward each otheralong the distal direction at an angle G. The angle G can be between 2degrees and 15 degrees, for instance between 5 degrees and 10 degrees,for instance approximately 7 degrees. Thus, the top and bottom surfaces30 d and 30 e can be geometrically configured to restore lordoticcurvature to the vertebral bodies. Alternatively, as illustrated inFIGS. 6K and 6M, the top and bottom surfaces 30 d and 30 e can beparallel to each other along the longitudinal direction L.

Referring now to FIG. 6A and FIGS. 7A-7E, either or both of the top andbottom surfaces 30 d and 30 e can be smooth or can include any surfacegeometry as desired. The surface geometry can increase the surface areaof the respective top and bottom surfaces 30 d and 30 e, therebypromoting bony ingrowth of the vertebral bodies into the top and bottomsurfaces 30 d and 30 e. Further, the surface geometry can increasefrictional forces between the top and bottom surfaces 10 d and 10 e andthe respective superior and inferior surfaces 14 a and 14 b, therebypromoting stabilization of the spacer 30 within the intervertebralspace. For instance, as illustrated in FIGS. 6A and 6D, the surfacegeometry can define elongate ridges 426. Each of the ridges 426 canextend out from a respective base 426 a to a respective peak 426 b. Theridges can be tapered from the base 426 a to the peak 426 b. Forinstance the peak 426 b can be a pointed peak or a rounded peak. Theridges 426 can be oriented parallel to each other, or angularly offsetwith respect to each other as desired. For instance, the ridges 426 canbe elongate along the lateral direction A, or any suitable alternativedirection as desired. For instance, the ridges 426 can be elongate alongthe longitudinal direction L. Alternatively, the ridges 426 can beelongate along a direction angularly offset with respect to each of thelateral direction A and the longitudinal direction L. The ridges 426 canextend between the side surfaces 30 c. For instance, the ridges 426 canextend from one of the side surfaces 30 c to the other of the sidesurfaces 30 c. The ridges 426 can further be oriented straight along thedirection of elongation or curved or bent as desired. The ridges 426 canbe spaced from each other uniformly or variably along a directionperpendicular to the direction of elongation of the ridges 426. Thus,the ridges 426 can be spaced from each other along the longitudinaldirection L. The direction of elongation can be determined by theorientation of the ridges when the ridges 426 are oriented straight.Alternatively, the direction of elongation can be determined by astraight line that extends from one of the terminal ends of the ridgesto the respective opposite terminal end of the ridges, for instance,when the ridges 426 are curved.

As illustrated in FIG. 6A, the ridges 426 can be disposed along anentirety of either or both of the top and bottom surfaces 30 d and 30 ealong a direction perpendicular to the direction of elongation. Forinstance, the ridges 426 can be arranged from the proximal end surface30 a to distal end surface 30 b. Alternatively, as illustrated in FIG.7A, the ridges 426 can be disposed along a portion of either or both ofthe top and bottom surfaces 30 d and 30 e. For instance, the ridges 426can be arranged along either or both of the top and bottom surfaces 30 dand 30 e of the spacer 30 at the cancellous spacer body 412, and not atthe cortical body portion 410. In one example, the ridges 426 can bearranged along a portion of the cancellous spacer body 412, forinstance, at a portion of the cancellous spacer body that does notinclude the engagement member 416. Alternatively, the ridges 426 can bearranged along an entirety of the cancellous spacer body 412.Alternatively or additionally, the ridges 426 can be arranged along aportion of the cortical spacer body 410.

Referring now to FIGS. 7B-7F. the surface geometry can alternatively oradditionally include spikes 428. For instance, each of the spikes 428can define a base 428 a and extend out from the base 428 a along thetransverse direction T to a peak 428 b. Thus, the spikes 428 at the topsurface 30 d can extend from the base 428 a to the peak 428 a in theupward direction, that is, away from the bottom surface 30 e. Similarly,spikes 428 at the bottom surface 30 e can extend from the base 428 a tothe peak 428 a in the downward direction, that is, away from the topsurface 30 d. The spikes 428 can be tapered from the base 428 a to thepeak 428 b. For instance the peak 428 b can be a pointed peak or arounded peak. The spikes 428 can be equidistantly spaced from each otheralong either or both of the lateral direction A and the longitudinaldirection L. Alternatively or additionally, the spikes 428 can be spacedfrom each other variably along either or both of the both of the lateraldirection A and the longitudinal direction L.

The spikes 428 can be arranged between the side surfaces 30 c, andfurther between the proximal end surface 30 a and the distal end surface30 b. For instance, as illustrated in FIG. 7B, the spikes 428 can bearranged from one of the side surfaces 30 c to the other of the sidesurfaces 30 c. Further, the spikes 428 can be arranged from the proximalend surface 30 a to the distal end surface 30 b. Thus, the spikes 428can be defined by both of the cortical spacer body 410 and thecancellous spacer body 412. Alternatively, the spikes 428 can be definedby one of the cortical spacer body 410 and the cancellous spacer body412. For example, as illustrated in FIG. 7C, the spikes 428 can bedisposed along a portion of either or both of the top and bottomsurfaces 30 c and 30 d. For instance, the spikes 428 can be arrangedalong either or both of the top and bottom surfaces 30 d and 30 e of thespacer 30 at the cancellous spacer body 412, and not at the corticalbody portion 410. In one example, the spikes 428 can be arranged along aportion of the cancellous spacer body 412, for instance, at a portion ofthe cancellous spacer body that does not include the engagement member416. Alternatively, the spikes 428 can be arranged along an entirety ofthe cancellous spacer body 412. Alternatively or additionally, thespikes 428 can be arranged along a portion of the cortical spacer body410. As illustrated in FIG. 7D, the spikes 428 can be arranged along thetop and bottom surfaces 30 d and 30 e of the entire cancellous spacerbody 412, and a portion of the cortical spacer body 410. For example,the portion of the cortical spacer body 410 can be a proximal portion ofthe cortical spacer body that abuts the cancellous spacer body 412,including the engagement member 414. Alternatively, the portion of thecortical spacer body 410 can be a distal portion of the cortical spacerbody 410 that is spaced from the cancellous spacer body 412.

The spikes 428 can be pyramidal in shape or can assume any alternativeshape as desired. In one example, the spikes 428 can define a pluralityof surfaces, and edges at the interfaces between adjacent ones of thesurfaces. As illustrated in FIG. 7B, the spikes 428 can be orientedsurface-to-surface. That is, at least some up to all of the surfaces ofat least some of the spikes 428 up to all of the spikes 428 face arespective surface of adjacent spikes 428 along either or both of thelongitudinal direction L and the lateral direction A. Alternatively, asillustrated in FIG. 7E, the spikes 428 can be oriented edge-to-edge.That is, at least some up to all of the edges of at least some of thespikes 428 up to all of the spikes 428 face a respective edge ofadjacent spikes 428 along either or both of the longitudinal direction Land the lateral direction A.

As illustrated in FIG. 7F, a first portion of the spacer 30 can includeridges 426, and a second portion of the spacer 30 different from thefirst portion can include spikes 428. The ridges 426 can be elongatealong the longitudinal direction L. For instance, the first portion canbe defined by the cortical spacer body 410, and the second portion canbe defined by the cancellous spacer body 412. In one example, the firstportion can include the cortical spacer body 410 and a portion of thecancellous spacer body 412. The portion of the cancellous spacer body412 can include the engagement member 416. The second portion caninclude a portion of the cancellous spacer body 412 that does notinclude the engagement member 416. Alternatively, the second portion caninclude an entirety of the cancellous spacer body 412. Alternativelystill, the second portion can be defined by the cortical spacer body410, and the first portion can be defined by the cancellous spacer body412. In one example, the second portion can include the cortical spacerbody 410 and a portion of the cancellous spacer body 412. The portion ofthe cancellous spacer body 412 can include the engagement member 416.The first portion can include a portion of the cancellous spacer body412 that does not include the engagement member 416. Alternatively, thefirst portion can include an entirety of the cancellous spacer body 412.It should be appreciated that while certain embodiments of the ridges426 and the spikes 428 have been described the ridges 426 and the spikes428 can be geometrically configured as desired, and arranged andoriented as desired. Further, it should be appreciated that while thesurface geometry has been described with respect to ridges and spikes,the surface geometry can be shaped in accordance with any suitablealternative embodiment as desired.

Referring now to FIGS. 8A-11D generally, it is recognized that thespacer 30 can be constructed in accordance with any suitable alternativegeometric configuration as desired. For instance, as illustrated inFIGS. 8A-8B, the first engagement member 414 of the cortical spacer body410 can be configured as a projection, and the second engagement member416 of the cancellous spacer body 412 can define a recess 419 that issized and configured to receive the first engagement member 414. Thefirst engagement member 414 can include a base 414 a and at least onewing 414 b such as a pair of wings 414 b that extend from the stem 414 ain the proximal direction, and project out with respect to the stem 414a in opposite directions away from each other along the lateraldirection A. The second engagement member 416 can include a base 416 aand a pair of necked portions 416 b that extend out from the base 416 ain the distal direction and project inward in opposite directions towardeach other along the lateral direction A. The wings 414 b can thus bedisposed between the necked portions 416 b and the base 416 a.Similarly, the necked portions 416 b can be disposed between the wings414 b and the base 414 a. Accordingly, the first engagement member 414is surrounded by the second engagement member 416 along the lateraldirection A and in the proximal direction. Otherwise stated, the secondengagement member 416 surrounds the first engagement member 414 alongthe lateral direction A and in the proximal direction.

Thus, as described above with respect to FIGS. 6A-6J, when the first andsecond engagement members 414 and 416 engage each other so as to jointhe cortical spacer body 410 to the cancellous spacer body 412, theengagement members 414 and 416 interfere with each other along both thelongitudinal direction L and the lateral direction A. The interferencethus prevents removal of the cortical spacer body 410 and the cancellousspacer body 412 along the longitudinal and lateral directions. Rather,in order to remove the cortical spacer body 410 and the cancellousspacer body 412 from each other, the cortical spacer body 410 and thecancellous spacer body 412 are moved with respect to each other alongthe transverse direction T until the engagement members 414 and 416 areremoved from interference with each other.

It should be appreciated that the cortical spacer body 410 can includepair of sides 430 that are spaced from each other along the lateraldirection A. The portions of the side surfaces 30 c that are defined bythe cortical spacer body 410 can be defined by respective different onesof the sides 430. Each of the sides 430 can further be spaced from thefirst engagement member 414 along the lateral direction A on oppositesides of the first engagement member 414. It can therefore be said thesides 430 flank opposed sides of the first engagement member 414 alongthe lateral direction A. Thus, the cortical spacer body 410 can definerespective voids between the sides 430 and the first engagement memberthat receives the necked portions 416 b of the cancellous spacer body412. It can thus be said that the cortical spacer body 410 can partiallysurround the cancellous body portion 412. The sides 430 can terminate ata location aligned with the projection of the first engagement member414 along the lateral direction A, as illustrated in FIG. 8A. Thus, thesides 430 can terminate at a location spaced in the distal directionfrom a lateral midline of the spacer 30 that divides the spacer intoequal lengths along the longitudinal direction L. Further, theprojection of the first engagement member 414 can terminate at alocation spaced in the distal direction from a lateral midline of thespacer 30 that divides the spacer into equal lengths along thelongitudinal direction L. Alternatively, as illustrated in FIG. 9A, thesides 430 can terminate at a location offset from the projection of thefirst engagement member 414 in the proximal direction. For instance, thesides 430 can terminate at a location spaced in the proximal directionfrom a lateral midline of the spacer 30 that divides the spacer intoequal lengths along the longitudinal direction L. The sides 430 canfurther terminate at a location spaced from the proximal end surface 30a in the distal direction. As illustrated in FIGS. 8B and 9B, the spacer30 can include the channel 418 and the force transfer member 424 asdescribed above with respect to FIGS. 6A-M.

As illustrated in FIGS. 8A-8B, the cortical spacer body 410 can define asurface area at each of the top and bottom surfaces 30 d and 30 e asdesired, for instance between 35 mm² and 60 mm², including between 40mm² and 50 mm², for instance approximately 46 mm². The cancellous spacerbody 412 can define a surface area at each of the top and bottomsurfaces 30 d and 30 e as desired, for instance between 50 mm² and 100mm², including between 70 mm² and 90 mm², for instance approximately 81mm². As illustrated in FIGS. 9A-9B, the cortical spacer body 410 candefine a surface area at each of the top and bottom surfaces 30 d and 30e as desired, for instance between 50 mm² and 80 mm², including between60 mm² and 70 mm², for instance approximately 62 mm². The cancellousspacer body 412 can define a surface area at each of the top and bottomsurfaces 30 d and 30 e as desired, for instance between 90 mm² and 120mm², including between 100 mm² and 110 mm², for instance approximately104 mm².

Referring now to FIGS. 10A-10B, the first engagement member 414 candefine a recess 419, and the second engagement member 416 be configuredas a projection 420 that is sized to be received in the recess 419.Otherwise sated, the recess 419 is sized to receive the projection 420.Thus, the recess 419 defined by the first engagement member 414 is sizedto receive the second engagement member 416. The first engagement member414 can include a base 414 a and a pair of necked portions 414 b thatextend out from the base 414 a in the distal direction and projectinward in opposite directions toward each other along the lateraldirection A. The base 414 a and the necked portions 414 b can define therecess 419. The recess 419 can extend through the cortical spacer body410 along the transverse direction T. The second engagement member 416can include a base 416 a and at least one wing 416 b, such as a pair ofwings 416 b, that extends from the stem 416 a in the proximal direction,and project out with respect to the stem 416 a in opposite directionsaway from each other along the lateral direction A. The wings 416 b canthus be disposed between the necked portions 414 b and the base 414 a.Similarly, the necked portions 414 b can be disposed between the wings416 b and the base 416 a. Accordingly, the second engagement member 416is surrounded by the first engagement member 414 along the lateraldirection A and in the distal direction. Otherwise stated, the firstengagement member 414 surrounds the second engagement member 416 alongthe lateral direction A and in the distal direction.

It should be appreciated that the cortical spacer body 410 can includepair of sides 430 that are spaced from each other along the lateraldirection A. The portions of the side surfaces 30 c that are defined bythe cortical spacer body 410 can be defined by respective different onesof the sides 430. Each of the sides 430 extend in the proximal directionfrom the necked portions on opposite lateral sides of the corticalspacer body 410. Thus, the cortical spacer body 410 can define a void434 between the sides 430 in the lateral direction that receives thebase 416 a, such that the wings are inserted into the recess 419. Thevoid 434 can thus define a lead-in, and can be open, to the recess 419along the distal direction. It can thus be said that the cortical spacerbody 410 can partially surround the cancellous body portion 412. Thesides 430 can terminate at a location spaced in the proximal directionfrom a lateral midline of the spacer 30 that divides the spacer intoequal lengths along the longitudinal direction L. The sides 430 canfurther terminate at a location spaced from the proximal end surface 30a in the distal direction. Alternatively, the sides 430 can terminate ata location offset from the projection of the first engagement member 414in the distal direction. For instance, the sides 430 can terminate at alocation spaced in the proximal direction from a lateral midline of thespacer 30 that divides the spacer into equal lengths along thelongitudinal direction L. As illustrated in FIGS. 8B and 9B, the spacer30 can include the channel 418 and the force transfer member 424 asdescribed above with respect to FIGS. 6A-M.

Thus, when the first and second engagement members 414 and 416 engageeach other so as to join the cortical spacer body 410 to the cancellousspacer body 412, the engagement members 414 and 416 interfere with eachother along both the longitudinal direction L and the lateral directionA. The interference thus prevents removal of the cortical spacer body410 and the cancellous spacer body 412 along the longitudinal andlateral directions. Rather, in order to remove the cortical spacer body410 and the cancellous spacer body 412 from each other, the corticalspacer body 410 and the cancellous spacer body 412 are moved withrespect to each other along the transverse direction T until theengagement members 414 and 416 are removed from interference with eachother. As illustrated in FIG. 10B, the spacer 30 can include the channel418 and the force transfer member 424 as described above with respect toFIGS. 6A-M.

As illustrated in FIGS. 10A-10B, the cortical spacer body 410 can definea surface area at each of the top and bottom surfaces 30 d and 30 e asdesired, for instance between 50 mm² and 80 mm², including between 60mm² and 70 mm², for instance approximately 62 mm². The cancellous spacerbody 412 can define a surface area at each of the top and bottomsurfaces 30 d and 30 e as desired, for instance between 90 mm² and 120mm², including between 100 mm² and 110 mm², for instance approximately104 mm².

Referring now to FIG. 11A-11B, the distal end surface 30 b can bedefined by the cortical spacer body 410, and the proximal end surface 30a is defined by the cancellous spacer body 412. For instance, thecortical spacer body 410 can define a cross member 440 that defines thedistal end surface 30 b. The cross member 440 defines an inner surface440 a and an outer surface 440 b opposite the inner surface 440 a. Theinner surface 440 a is configured to abut a distal end surface of thecancellous spacer body 412, and the outer surface 440 b is configured toface the frame 26 when the frame 26 is attached to the spacer 30. Thecross member 440 further defines opposed ends that are opposite eachother along the lateral direction A, and first and second arms 442 thatextend along the proximal direction from respective different ones ofthe opposed ends. The arms 442 can thus define sides 430 of the corticalspacer body 410 that are spaced from each other along the lateraldirection A. Each of the arms 442 defines a respective inner surface 442a and an outer surface 442 b opposite the inner surface 442 a. The innersurfaces 442 a are configured to abut opposed side surfaces of thecancellous spacer body 412 that are spaced from each other along thelateral direction A. The arms 442 can extend along an entirety of thelength of the side surfaces 30 c, and can terminate at a locationsubstantially flush with the proximal end surface 30 a. Accordingly, thecortical spacer body 410 can partially surround the cancellous spacerbody 412. In particular, the cortical spacer body 410 can surround allsides of the cancellous spacer body, with the exception of the proximalend surface 30 a, along a plane that is defined by the longitudinaldirection L and the lateral direction A. Alternatively, the corticalspacer body 410 can further extend along the proximal end 30 a, suchthat the cortical spacer body 410 entirely surrounds the cancellous bodyportion 412 along the plane that is defined by the longitudinaldirection L and the lateral direction A. Thus, it can be said that thecortical spacer body 410 at least partially surrounds the cancellousbody portion 412.

The spacer 30 further defines the channel 418 that extends through thecancellous spacer body 412. The channel 418 can terminate at thecortical spacer body 410. Alternatively, the channel 418 can extend atleast into the cortical spacer body 410. For instance, the channel 418can terminate in the cortical spacer body 410. Alternatively, thechannel 418 can extend through the cortical spacer body 410. The channel418 can have a first opening 418 a defined by the proximal end surface30 a. Accordingly, the channel 418 can have a first end defined by thefirst opening 418 a. The first opening 418 a can be an enclosed opening.That is, the first opening 418 a can be enclosed by the proximal endsurface 30 a along a plane defined by the lateral direction A and thetransverse direction T. The first opening 418 a can be sized to receivethe abutment member 73 of the frame 26 when the frame 26 is attached tothe spacer 30. Thus, the abutment member 73 can extend from the firstopening 418 a into the channel 418 in the distal direction.

The channel 418 has a second end opposite the first end. The second endof the channel 418 can be terminate within the cortical spacer body 410,such that the first opening 418 a is the only opening of the aperture.Alternatively, the second end of the channel 418 can terminate at thecortical spacer body 410, such that the second end 418 b is defined bythe cancellous spacer body 412. Alternatively still, the channel 418 canextend through the cortical spacer body 410. Further, the spacer 30further includes the force transfer member 424 that is configured to beinserted into the channel 418 as described above. Thus, the channel 418is sized and configured to receive the force transfer member 424. Whenthe force transfer member 424 is disposed in the channel 418, the firstend 424 a can be positioned adjacent the first opening 418 a. In oneexample, the first end 424 a can be recessed with respect to the firstopening 418 a along the distal direction. In another example, the firstend 424 a can be flush with the proximal end surface 30 a. Thus, thefirst end 424 a can define a surface geometry that matches the surfacegeometry of the proximal end surface 30. As described above, theabutment member 73 can contact the first end 424 a when the frame 26 isattached to the spacer 30, and the force transfer member 424 is disposedin the channel 418. For instance, the first opening 418 a can be sizedto receive the abutment member 73 of the frame 26 when the frame 26 isattached to the spacer 30. Thus, the abutment member 73 can extend fromthe first opening 418 a into the channel 418 and abut the first end 424a of the force transfer member 424, for instance along the longitudinaldirection L.

Further, when the force transfer member 424 is disposed in the channel418, the second end 424 b can be in contact with the cortical spacerbody 410. For instance, the second end 424 b can abut the corticalspacer body 410 along the longitudinal direction L. Alternatively, thesecond end 424 b can be embedded in the cortical spacer body 410.Alternatively still, the second end 424 b can be flush with the distalend surface 30 b. Thus, the second end 424 b can be in abutment contactwith the cortical spacer body 410 along the longitudinal direction L.Alternatively or additionally, the second end 424 b can be in press fitcontact with the cortical spacer body 410.

During operation, as the intervertebral implant 22 is inserted into theintervertebral space, the outer surface 54 of the body 46 of the supportmember 34 may be impacted by an impaction tool or the like in order toadvance the implant 22 into the intervertebral space. Because theabutment member 73 is in contact with the force transfer member 424, forinstance in abutment contact or in press-fit contact, or both, impactionforces is transferred from the frame 26, to the force transfer member424, through the force transfer member 424, and to the cortical spacerbody 410. Thus, though the support member 34 is positioned adjacent thecancellous spacer body 412, a substantial majority up to a substantialentirety of the impaction forces are absorbed by the cortical spacerbody 412, which has a rigidity greater than that of the cancellousspacer body 412.

As described above, the spacer body 30 defines a pair of side surfaces30 c. As illustrated in FIG. 11A, the spacer 30 can include anattachment channel 444 that can extend through the cortical spacer body410 and into the cancellous spacer body 412 along a direction that isangularly offset with respect to the force transfer channel 418. Inaccordance with one embodiment, the attachment channel 444 include afirst segment 444 a that extends from a first one of the side surfaces30 c toward the second one of the side surfaces 30 c, and terminatesprior to intersecting the force transfer channel 418. The attachmentchannel 444 can include a second segment 444 b that extends from thesecond one of the side surfaces 30 c toward the first one of the sidesurfaces 30 c, and terminates prior to intersecting the force transferchannel 418. The first and second segments 444 a and 444 b can be joinedso as to intersect the force transfer channel 418. The spacer 30 canfurther include at least one coupling member 446 that is sized to beinserted into the attachment channel 444. Thus, the at least onecoupling member 446 extends through one of the respective arms 442 andinto the cancellous spacer body 412 in the attachment channel 444. Inone example, the spacer 30 includes a first coupling member 446 thatextends into the first segment 444 a through a first respective one ofthe arms 442 and into the cancellous spacer body 412. The spacer 30 canfurther include a second coupling member 446 that extends into thesecond segment 444 b through a second respective one of the arms 442 andinto the cancellous spacer body 412. The coupling members 446 areelongate along a length that is less than the distance from therespective side surface 30 c and the force transfer channel 418.Accordingly, the coupling members 446 attach the cortical spacer body410 to the cancellous spacer body 412. Further the coupling members 446avoid mechanical interference with the force transfer member 424 do notinterfere with each other.

The spacer body 30 can further include the frame 26 having the supportmember 34 and the first and second arms 38 and 42 that extend out fromthe support member in the proximal direction as described above. Thesupport member 34 is configured to abut the proximal end surface 30 a,and the arms 38 and 42 are configured to abut and extend alongrespective different ones of the side surfaces 30 c. The arms 38 and 42can extend along the respective ones of the side surfaces 30 c past thecortical spacer body 410 and can terminate at the cancellous spacer body412. The retention members 116 of the frame 26 that extend in from eachof the arms 38 and 42 can extend into respective side surfaces 30 c inthe manner as described above with respect to FIGS. 2C-2F. For instance,the at least one retention member 116 that extends from the first arm 38can extend into the first segment 444 a. The at least one retentionmember 116 that extends from the second arm 42 can extend into thesecond segment 444 a. Alternatively, the arms 38 and 42 can extend alongan entirety of the length of the side surfaces 30 c from the proximalend surface 30 a to the distal end surface 30 b, and can terminate at alocation substantially flush with the proximal end surface 30 a.

As described above with respect to FIGS. 11A-B, the arms 442 can extendalong an entirety of the length of the side surfaces 30 c, and canterminate at a location substantially flush with the proximal endsurface 30 a. Alternatively, as illustrated in FIGS. 11C-D, the arms 442can extend along a portion of the length of the side surfaces 30 c, andcan terminate at a location spaced from the proximal end surface 30 a.Thus, the cortical spacer body 410 can at least partially surround thecancellous spacer body 412. The cortical spacer body 410 can includerespective engagement members 414 in the form of the retention members116 that project inward from each of the arms 442 toward the other oneof the arms. The cancellous spacer body 412 can include respectiveengagement members 416 configured as recesses 419 that are sized andconfigured to receive the engagement members 414 so as to couple thecortical spacer body 410 to the cancellous spacer body 412. Asillustrated in FIGS. 11C-D, and FIGS. 6A-10B, the cortical spacer body410 can be flush with the cancellous spacer body 412 at the respectiveside surfaces 30C. As illustrated in FIG. 11D, the frame 26 can beattached to the spacer 30 as described above with respect to FIG. 11B.While the cortical spacer body 410 can partially surround the cancellousspacer body 412 as described herein, it should be appreciated that thecortical spacer body 410 can entirely surround the cancellous spacerbody 412 as desired. Thus, it can be said that the cortical spacer body410 can at least partially surround the cancellous spacer body 412.

Referring now to FIGS. 12A-12D, the spacer 30 can be constructed inaccordance with an alternative embodiment. As described above, thespacer can define a proximal end surface 30 a and a distal end surface30 b that is spaced from the proximal end surface 30 a along thelongitudinal direction L. For instance, the distal end surface 30 b isspaced from the proximal end surface 30 a in the distal direction. Thus,the distal end surface 30 b can be spaced from the proximal end 30 a inthe insertion direction of the spacer 30 into the intervertebral space.Accordingly, the distal end surface 30 b is spaced from the proximal end30 a in the insertion direction of the intervertebral implant 22 intothe intervertebral space. It should be appreciated that, when theimplant 22, and thus the spacer 30, is implanted in the intervertebralspace, the distal end surface 30 b can be spaced posteriorly from theproximal end surface 30 a. Alternatively, as described above, the spacer30, and thus the intervertebral implant 22, can be inserted in theintervertebral space along an insertion direction that is in the lateraldirection or the oblique direction.

The spacer 30 further defines a pair of opposed side surfaces 30 cspaced from each other along the lateral direction A. Each of the sidesurfaces 30 c further extends from the proximal end surface 30 a to thedistal end surface 30 b. When the frame 26 is attached to the spacer 30(see FIGS. 2A-B), the support member 34 can extend along the proximalend surface 30 a, and the arms 38 and 42 can extend along at least aportion up to an entirety of the length along the longitudinal directionL of respective different ones of the sides 30 c. It should beappreciated that the surfaces 30 a-30 e can be sized and shaped asdesired. For instance at least one or more up to all of the surfaces 30a-30 e can be planar, curved, bent, or otherwise non-planar as desired.

The spacer 30 further defines a top surface 30 d and a bottom surface 30e spaced from the top surface 30 d along the transverse direction T. Forinstance, the top surface 30 d is spaced upward with respect to thebottom surface 30 e. Thus, the top surface 30 d is configured to facethe superior vertebral surface 14 a of the superior vertebral body 10 a,and contact the superior vertebral surface 14 a of the superiorvertebral body 10 a. The bottom surface 30 e is configured to face theinferior vertebral surface 14 b of the inferior vertebral body 10 b, andcontact the inferior vertebral surface 14 b of the inferior vertebralbody 10 b. The spacer 30 can define a height from the top surface 30 cto the bottom surface 30 d in the transverse direction T. The spacer canfurther define a length from the proximal end surface 30 a to the distalend surface 30 b in the longitudinal direction. The distal end surface30 b can define a first width along the lateral direction A that is lessthan a second width along the lateral direction A of the proximal endsurface 30 a. Each of the first and second widths can extend along thelateral direction A from one of the side surfaces 30 c to the other ofthe side surfaces 30 c. At least one or both of the first and secondwidths can be greater than the height and less than the length.

As described above, the spacer 30 can be made from a bone graft materialsuch as allograft bone, autograft bone, or xenograft bone, for example.For instance, the spacer 30 can include a cortical spacer body 410 and acancellous spacer body 412. The cortical spacer body 410 can define atleast a portion up to an entirety of the distal end surface 30 b. Thecancellous spacer body 412 can define at least a portion of the proximalend surface up to an entirety of the proximal end surface 30 a. It willbe appreciated, as described above, that at least one, such as each, ofthe fixation members, which can be configured as screws, that isinserted through the fixation element receiving aperture 58 (see FIGS.3A-3C) toward the spacer 30 travels from the support member 34 andthrough the cancellous spacer body 412, and thus through the cancellousbone graft material, without passing through cortical spacer body 410,and thus without passing through any of the cortical bone graftmaterial. Thus, a straight line passing centrally through the fixationelement receiving apertures 58 is aligned with the cancellous spacerbody 412 without first passing through the cortical spacer body 410.

For instance, as illustrated in FIG. 12E, each of the fixation memberscan extend through the cancellous spacer body 412 so as to define arespective bone fixation channel 413 that extends through the cancellousspacer body 412. The bone fixation channel 413 can have a perimeter 421that is defined by the cancellous spacer body 412. The perimeter 421defined by the cancellous spacer body 412 can be arc-shaped. Thechannels 413 can include at least one first channel 413 a, such as apair of first channels 413 a. The at least one first channel 413 a candefine a front opening 417 a in the proximal end surface 30 a, and a topopening 417 b in the top surface 30 d. The front opening 417 a can beopen at an intersection of the proximal end surface 30 a and the topsurface 30 d. Accordingly, a length of the at least one first bonefixation channel 413 a can be defined at a location distal of the frontopening 417 a. Further, the length of the at least one first bonefixation channel 413 a can be open along both 1) in a superior directionthat extends from the bottom surface 30 e to the top surface 30 d, and2) a proximal direction that is opposite the distal direction at alocation distal of the front opening 417 a in the proximal end surface30 a.

Similarly, the channels 413 can include at least one second channel 413b, such as a pair of second channels 413 b. The at least one secondchannel 413 b can define a front opening 417 c in the proximal endsurface 30 a, and a bottom opening 417 d in the bottom surface 30 e. Theat least one second channel 413 b can be open at an intersection of theproximal end surface 30 a and the bottom surface 30 e. Accordingly, alength of the at least one second bone fixation channel 413 b can bedefined at a location distal of the front opening 417 c. Further thelength of the at least one second bone fixation channel 413 b can beopen along both 1) in an inferior direction that extends from the topsurface 30 d to the bottom surface 30 e, and 2) the proximal directionat a location distal of the front opening 417 c in the proximal endsurface 30 a.

Alternatively, as illustrated in FIG. 12F, the front opening 417 a ofthe at least one first channel 413 a can be fully encircled by thecancellous spacer body 412 at the proximal end surface 30 a. Thus, anentirety of the front opening 417 a can be spaced from the top surface30 d along the inferior direction. Similarly, the top opening can befully encircled by the cancellous spacer body 412 at the top surface 30d. Thus, the top opening can be spaced from the proximal end surface 30a along the distal direction. It should therefore be appreciated thatthe at least one first channel 413 a can be fully encircled by thecancellous spacer body 412 along an entirety of its length from thefront opening 413 a to the top opening. Furthermore, the front opening417 c of the at least one second channel 413 b can be fully encircled bythe cancellous spacer body 412 at the proximal end surface 30 a. Thus,an entirety of the front opening 417 c can be spaced from the bottomsurface 30 e along the superior direction. Similarly, the bottom openingcan be fully encircled by the cancellous spacer body 412 at the topsurface 30 d. Thus, the bottom opening can be spaced from the proximalend surface 30 a along the distal direction. It should therefore beappreciated that the at least one second channel 413 b can be fullyencircled by the cancellous spacer body 412 along an entirety of itslength from the front opening 413 c to the bottom opening.

Referring again to FIGS. 12A-12D, the cortical spacer body 410 canfurther define a first portion of one or both of the side surfaces 30 c,and the cancellous spacer body 412 can define a second portion of one orboth of the side surfaces 30 c. At least some of the first portion ofthe side surfaces 30 c can be distal with respect to the second portionof the side surfaces 30 c. For instance, the cortical spacer body 410can define laterally opposed arms 423 that extend proximally along theopposed sides 30 c, respectively, to the proximal end surface 30 a.Thus, respective ends of the opposed arms 423 can be flush with thecancellous spacer body 412 at the proximal end surface 30 a. Thecancellous spacer body 412 can define laterally opposed recesses 425that extend through the proximal end surface 30 a and are sized toreceive the opposed arms 423, respectively. Accordingly, the corticalspacer body 412 at the proximal end surface 30 a can abut the supportmember of the frame. Thus, impaction forces in the insertion directionagainst the support member of the frame 26 that urge the implant to beinserted into the intervertebral space can be transferred from the frame26 to the cortical spacer body 410 at the arms 423. Further, the arms423 can define engagement members 427 that are configured to receive aninsertion instrument that inserts the spacer 30 into the intervertebralspace without the frame 26. Further, the cortical spacer body 410 canfurther define a first portion of either or both of the top and bottomsurfaces 30 d and 30 e. The cancellous spacer body 412 can define asecond portion of either or both of the top and bottom surfaces 30 d and30 e. The first portion of the top and bottom surfaces 30 d and 30 e canbe distal with respect to the second portion of the top and bottomsurfaces 30 d and 30 e.

The cortical spacer body 410 and the cancellous spacer body 412 areconfigured to abut each other so as to define the spacer 30. Forinstance, the cortical spacer body 410 can include an engagement member414, and the cancellous spacer body 412 can include an engagement member416 that is configured to engage with the engagement member 414 of thecortical spacer body 410 so as to join the cortical spacer body 410 tothe cancellous spacer body 412. In this regard, the engagement member414 of the cortical spacer body 410 can be referred to as a firstengagement member, and the engagement member 416 of the cancellousspacer body 412 can be referred to as a second engagement member. Thefirst engagement member 414 can be disposed distal with respect to thesecond engagement member 416. Further, the first and second engagementmembers 414 and 416 can overlap along the longitudinal direction L suchthat a straight line that extends in the distal direction from theproximal end surface 30 a can pass through both the first engagementmember 414 and the second engagement member 416.

In accordance with one embodiment, the first engagement member 414 candefine a recess 419, and the second engagement member 416 be configuredas a projection 420 that is sized to be received in the recess 419.Otherwise sated, the recess 419 is sized to receive the projection 420.Thus, the recess 419 defined by the first engagement member 414 is sizedto receive the second engagement member 416. The recess 419 can extendthrough the cortical spacer body 410 along the transverse direction T.Accordingly, the second engagement member 416 is surrounded by the firstengagement member 414 along the lateral direction A and in the distaldirection. Otherwise stated, the first engagement member 414 surroundsthe second engagement member 416 along the lateral direction A and inthe distal direction. It can thus be said that the cortical spacer body410 can partially surround the cancellous body portion 412.Alternatively, the first engagement member 414 can be configured as aprojection, and the second engagement member can be configured as arecess that receives the projection.

The spacer 30 further defines a force transfer channel 418 that extendsthrough the cancellous spacer body 412 and the cortical spacer body 410along the lateral direction A. Thus, the first opening 418 a of thechannel 418 can be defined by one of the side surfaces 30 c, and thesecond opening 418 b of the channel 418 can be defined by the other ofthe side surfaces 30 c. In one embodiment, one or both of the first andsecond openings 418 a and 418 b can be defined by the cortical spacerbody 410. In another embodiment, one or both of the first and secondopenings 418 a and 418 b can be defined by the cancellous spacer body412. The first and second openings 418 a can be defined by enclosedperimeters. A first portion of the channel 418 can further be defined bycancellous spacer body 410. For instance, the first portion of thechannel 418 can extend from each of the respective sides 30 c to therecess 419. A second portion the channel 418 can be defined by thecancellous spacer body 412. For instance, the second portion can bedefined by the projection 420.

As illustrated in FIG. 12A, the spacer 30 can define a plurality ofgrooves 415 that can extend into the side surfaces 30 c at the corticalspacer body 410, and the distal end surface 30 b. The grooves 415 canextend at least into the spacer 30 along the transverse direction T, andcan extend through the spacer 30 along the transverse direction T. Theretention members 116 supported by the first arm 38 (see, e.g., FIG. 3A)are configured to be inserted into the grooves 415 at a first one of theside surfaces 30 c. The retention members 116 supported by the secondarm 42 are configured to be inserted into the grooves 415 at the secondone of the side surfaces 30 c. Alternatively, the spacer can be devoidof the grooves 415, such that the retention members 116 bite into theside surface 30 c so as to create respective recesses that retain theretention members in the cortical spacer body 410. Alternatively, thefirst and second arms 38 and 42 can extend around the side surfaces andterminate at the distal end surface 30 b. Thus, as described above, itshould be appreciated that the frame is configured to secure thecancellous spacer body 412 at a location between the support member 34of the frame 26 and the cortical spacer body 410.

With continuing reference to FIGS. 12A-12D, the spacer 30 furtherincludes a force transfer member 424 that is configured to be insertedinto the channel 418. Thus, the channel 418 is sized and configured toreceive the force transfer member 424. The force transfer member 424 canbe made of any suitable biocompatible material having a hardness greaterthan the cancellous spacer body 412. For instance, the force transfermember 424 can be made of cortical bone, titanium, steel, PEEK, apolymer, ceramics, chronOs, CoCr (or other implantable metals), ultrahigh molecular weight polyethylene (UHMWPE), poly ether ether ketone(PEKK), Carbon-fiber reinforced poly ether ether ketone (PEEK), othersuitable implantable polymers, or the like. When the force transfermember 424 is disposed in the channel 418, the force transfer member 424can secure the cortical spacer body 410 to the cancellous spacer body412.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. Furthermore, it should be appreciated thatthe structure, features, and methods as described above with respect toany of the embodiments described herein can be incorporated into any ofthe other embodiments described herein unless otherwise indicated. It isunderstood, therefore, that this invention is not limited to theparticular embodiments disclosed, but it is intended to covermodifications within the spirit and scope of the present disclosure.Further, it should be appreciated, that the term substantially indicatesthat certain directional components are not absolutely perpendicular toeach other and that substantially perpendicular means that the directionhas a primary directional component that is perpendicular to anotherdirection.

What is claimed:
 1. An intervertebral implant configured to be insertedinto an intervertebral space, the intervertebral implant comprising: aspacer including: a cortical spacer body comprising a cortical bonegraft material; a cancellous spacer body comprising a cancellous bonegraft material, the cancellous spacer body disposed proximal withrespect to at least a portion of the cortical spacer body, wherein thespacer defines a proximal end that comprises the cancellous spacer bodyand none of the cortical spacer body, and a distal end that is spacedfrom the proximal end in a distal direction, the distal end comprisingthe cortical spacer body and none of the cancellous spacer body; and aframe including a support member disposed proximal with respect to thecancellous spacer body and configured to extend along a portion of thecancellous spacer body, such that the cancellous spacer body is disposedbetween the support member and the at least a portion of the corticalspacer body, wherein the frame defines at least one fixation elementreceiving aperture that extends through the support member, such that afixation element inserted through the fixation element receivingaperture toward the spacer travels from the support member and throughthe cancellous bone graft material without passing through any of thecortical bone graft material.
 2. The intervertebral implant as recitedin claim 1, wherein the frame further includes first and second opposedarms that extend from the support member and are configured to engagethe cortical spacer body.
 3. The intervertebral implant as recited inclaim 2, wherein the frame includes at least one retention member thatextends from the first arm along a direction toward the second arm, andat least one retention member that extends out from the second arm alonga direction toward the first arm, and the cortical spacer body isconfigured to receive the retention members so as to attach the frame tothe spacer.
 4. The intervertebral implant as recited in claim 3, whereinthe cortical spacer body defines at least one groove sized to receivethe at least one retention member.
 5. The intervertebral implant asrecited in claim 3, wherein the at least one retention member isconfigured to bite into the cortical spacer body so as to create arecess that retains the at least one retention member.
 6. Theintervertebral implant as recited in claim 1, wherein the spacerincludes opposed side surfaces spaced from each other along a lateraldirection that is perpendicular to the distal direction, wherein theintervertebral implant is configured for insertion in the distaldirection, wherein the distal direction is oriented along a lateralapproach, an anterior-posterior approach, or an oblique approach intothe intervertebral space.
 7. The intervertebral implant as recited inclaim 6, wherein the distal end has a width along the lateral directionfrom one of the side surfaces to the other of the side surfaces, theproximal end has a width along the lateral direction from one of theside surfaces to the other of the side surfaces, and the width of thedistal end is less than the width of the proximal end.
 8. Theintervertebral implant as recited in claim 1, wherein the frame definesfour fixation element receiving apertures that extend through thesupport member, such that four fixation elements that are insertedthrough respective ones of the four fixation element receiving aperturesand pass entirely through the spacer travel through the cancellous bonegraft material without passing through any of the cortical bone graftmaterial.
 9. An intervertebral implant assembly comprising: theintervertebral implant as recited in claim 8; and the fixation elementsas recited in claim
 8. 10. The intervertebral implant as recited inclaim 1, wherein the at least one fixation element receiving aperturecomprises a plurality of fixation element receiving apertures thatextends through the support member, and all fixation elements that areinserted through respective ones of the fixation element receivingapertures pass entirely through the spacer travel through the cancellousbone graft material without passing through any of the cortical bonegraft material.
 11. An intervertebral implant comprising: a spacerincluding a cortical spacer body that comprises a cortical bone graftmaterial, and a cancellous spacer body that comprises a cancellous bonegraft material; and a frame including a support member configured toextend along a portion of the cancellous spacer body, the frame furtherincluding first and second opposed arms that extend from the supportmember and are configured to engage the cortical spacer body; whereinthe frame defines at least one fixation element receiving aperture thatextends through the support member, such that a fixation elementinserted through the fixation element receiving aperture toward thespacer travels from the support member and through the cancellous bonegraft material without passing through any of the cortical bone graftmaterial, and wherein the spacer defines a proximal end surface and adistal end surface opposite the proximal end surface in a distaldirection, the proximal end surface comprising the cancellous spacerbody and none of the cortical spacer body, and the distal end surfacecomprising the cortical spacer body and none of the cancellous spacerbody.
 12. The intervertebral implant as recited in claim 11, wherein 1)the spacer defines a top surface that extends from the proximal endsurface to the distal end surface, and a bottom surface opposite the topsurface, the bottom surface extending from the proximal end surface tothe distal end surface, 2) the at least one fixation element creates atleast one channel in the cancellous spacer body after it extends throughthe at least one fixation element receiving aperture, and 3) the atleast one channel defines a first opening in the proximal end surfaceand a second opening in the top surface.
 13. The intervertebral implantas recited in claim 12, wherein the spacer further defines a pair ofopposed side surfaces that extend between the proximal end surface andthe distal end surface, the opposed side surfaces spaced from each otheralong a lateral direction, the distal end surface has a width along thelateral direction from one of the side surfaces to the other of the sidesurfaces, the proximal end surface has a width along the lateraldirection from one of the side surfaces to the other of the sidesurfaces, and the width of the distal end is less than the width of theproximal end.
 14. The intervertebral implant as recited in claim 12,wherein the first opening is completely encircled by the proximal endsurface.
 15. The intervertebral implant as recited in claim 12, whereinthe at least one channel is open at an intersection of the proximal endsurface and the top surface.
 16. The intervertebral implant as recitedin claim 12, wherein the at least one channel is open at an intersectionof the proximal end surface and the bottom surface.
 17. Anintervertebral implant assembly comprising: a spacer including acortical spacer body comprising a cortical bone graft material, and acancellous spacer body comprising a cancellous bone graft material,wherein the cortical spacer body at least partially surrounds thecancellous spacer body, such that a proximal end of the spacer comprisesthe cancellous spacer body and none of the cortical spacer body, and adistal end of the spacer comprises the cortical spacer body and none ofthe cancellous spacer body, the distal end opposite the proximal end ina distal direction; a frame including a support member and first andsecond opposed arms that extend from the support member and areconfigured to engage the cortical spacer body so as to retain the spacerin a void that is defined by the support member and the first and secondopposed arms; and an expansion instrument including a first base and afirst expansion arm that extends from the first base and is configuredto be attached to the first arm of the frame, and a second base and asecond expansion arm that extends from the second base and is configuredto be attached to the second arm of the frame, wherein the first baseand the first expansion arm are separate from the second base and thesecond expansion arm, and a portion of one of the first and second basesis translatable in a portion of the other of the first and second basesas the first and second bases translate with respect to each other intheir respective entireties so as to cause movement of at least one ofthe first and second expansion arms relative to the other of the firstand second expansion arms, which in turn causes the respective at leastone of the first and second arms of the frame to flex away from theother of the first and second arms of the frame.
 18. The intervertebralimplant assembly as recited in claim 17, wherein the first expansion armdefines a projection that is inserted into a receiving aperture of thefirst arm of the frame, so as to attach the first expansion arm to thefirst arm of the frame, and the second expansion arm defines aprojection that is inserted into a receiving aperture of the second armof the frame, so as to attach the second expansion arm to the second armof the frame.
 19. The intervertebral implant assembly as recited inclaim 17, wherein the first expansion arm is monolithic with the firstbase, and the second expansion arm is monolithic with the second base.20. The intervertebral implant assembly as recited in claim 17, whereinthe first expansion arm is coupled to the first base, and the secondexpansion arm is coupled to the second base.
 21. The intervertebralimplant assembly as recited in claim 17, wherein the cancellous spacerbody is disposed proximal with respect to at least a portion of thecortical spacer body, and the support member is disposed proximal withrespect to the cancellous spacer body and configured to extend along aportion of the cancellous spacer body, such that the cancellous spacerbody is disposed between the support member and the at least a portionof the cortical spacer body.
 22. The intervertebral implant assembly asrecited in claim 21, wherein the frame defines at least one fixationelement receiving aperture that extends through the support member, suchthat a fixation element inserted through the fixation element receivingaperture toward the spacer travels from the support member and throughthe cancellous bone graft material without passing through any of thecortical bone graft material.
 23. The intervertebral implant assembly asrecited in claim 22, wherein the spacer includes opposed sides spacedfrom each other along a lateral direction that is perpendicular to thedistal direction, wherein the intervertebral implant is configured forinsertion in the distal direction, wherein the distal direction isoriented along a lateral approach, an anterior-posterior approach, or anoblique approach into the intervertebral space.
 24. The intervertebralimplant assembly as recited in claim 23, wherein the cortical spacerbody and the cancellous spacer body define an interface therebetween ateach of the opposed sides between the proximal end and the distal end.25. The intervertebral implant assembly as recited in claim 22,wherein 1) the spacer defines a proximal end surface, a distal endsurface, a top surface that extends from the proximal end surface to thedistal end surface, and a bottom surface opposite the top surface, thebottom surface extending from the proximal end surface to the distal endsurface, 2) the at least one fixation element creates at least onechannel in the cancellous spacer body after it extends through the atleast one fixation element receiving aperture, and 3) the at least onechannel defines a first opening in the proximal end surface and a secondopening in the top surface.
 26. The intervertebral implant assembly asrecited in claim 25, wherein at least a portion of the proximal endsurface is defined by the cancellous spacer body.
 27. The intervertebralimplant assembly as recited in claim 25, wherein the spacer furtherdefines a pair of opposed side surfaces that extend between the proximalend surface and the distal end surface, the opposed side surfaces spacedfrom each other along a lateral direction, the distal end surface has awidth along the lateral direction from one of the side surfaces to theother of the side surfaces, the proximal end surface has a width alongthe lateral direction from one of the side surfaces to the other of theside surfaces, and the width of the distal end is less than the width ofthe proximal end.
 28. The intervertebral implant assembly as recited inclaim 25, wherein the first opening is completely encircled by theproximal end surface.
 29. The intervertebral implant assembly as recitedin claim 25, wherein the at least one channel is open at an intersectionof the proximal end surface and the top surface.
 30. The intervertebralimplant assembly as recited in claim 25, wherein the at least onechannel is open at an intersection of the proximal end surface and thebottom surface.
 31. The intervertebral implant assembly as recited inclaim 17, wherein the frame includes at least one retention member thatextends from the first arm along a direction toward the second arm, andat least one retention member that extends out from the second arm alonga direction toward the first arm, and the cortical spacer body isconfigured to receive the retention members so as to attach the frame tothe spacer.
 32. The intervertebral implant assembly as recited in claim31, wherein the cortical spacer body defines at least one groove sizedto receive a respective one of the at least one retention members. 33.The intervertebral implant assembly as recited in claim 31, wherein arespective one of the at least one retention members is configured tobite into the cortical spacer body so as to create a recess that retainsthe respective one of the at least one retention members.